Quantification of Burial Mounds in Yambol District, Ancient Thrace*

doi: 10.2143/AWE.15.0.3167466 AWE 15 (2016) 113-127

Barbora Weissova

Abstract The present study compiles results from the Burial Mounds Project (BUM), which verified nearly 500 features in Yambol district. The macro-regional study focuses on the quantification of burial mounds in the entire district. The number is further refined by the micro-regional study in Elkhovo municipality, part of the macro-region. The results enable us to consider the pros and cons of utilising topographical maps of different scales and satellite imagery for determining mounds. The study also attempts to quantify the rate and the speed of the decline of the burial mounds as well as to identify major factors contributing to their decay.

The territory of Ancient Thrace is well known for its abundance of burial mounds, which, with varying density, spread all over the landscape. This phenomenon, however, lacks any further archaeological instantiation and quantification. Numerous studies focus on excavation results of burial mounds as individual features,1 mainly describing grave-goods and architectural remains if present.2 None of them deter- mines general characteristics that would contribute to the quantification of burial mounds throughout the whole territory. This study is meant to be the first step towards such a systematic quantification, determining the most suitable approach for the procedure on the basis of macro- and micro-regional study within the Yam- bol district of present-day Bulgaria.

* The study was supported by the Grants Agency of Charles University, Prague, as part of the project ‘Spatial Relations of Flat Settlements and Burial Mounds in Exquisite Areas of Thrace’, GA UK no. 626314. 1 All archaeologically excavated mounds are published in annual short reports in Arheologicheski otkritya i razkopki (AOR) by the Bulgarian Academy of Sciences. 2 Beyond the brief reports in AOR, studies and interpretations of diverse funerary aspects have been published in numerous Bulgarian periodicals and in many monographs and other publications. These are beyond the scope of the present study which targets solely quantification methods. 114 B. Weissova

Introduction to the BUM Project The BUM project focuses on prediction, verification in the terrain, spatial analysis, interpretation and chronology of burial mounds in Bulgaria,3 namely in the districts of Yambol, Stara Zagora and Pazardzhik. In the Yambol and Stara Zagora districts, the project has been running as an inherent part of interdisciplinary field research undertaken by the Tundzha Regional Archaeological Project (TRAP).4 In the Pazardzhik district, an independent campaign was conducted in 2011.5 A preliminary report on the results from all the three districts was published in 2013;6 up to now, only the Pazardzhik district has been individually assessed in a brief report.7 The following study involves results of surveys conducted in 2009 and 2010 in the Yambol district and includes also several refinements made during 2014. The expeditions took place with the devoted support of local specialists from the History Museum of Yambol8 and with the great effort of many students from all over the world.9

Previous Studies Quantifying Burial Mounds in Bulgaria Burial mounds form an essential part of the Thracian landscape and local cultural heritage. Their overall abundance, the potential value of their contents10 and their cultural importance11 have been discussed in numerous studies. However, most

3 Burial mounds appeared in the north-eastern part of Thrace in the Early Bronze Age (4th/3rd millennia BC) (Panaiotov 1989, 50–51) and become widespread all over Thrace during the Iron Age (Archibald 1998, 151). Subsequent decline in their use is dated to the 4th century AD (Valcheva 1996, 94). 4 TRAP was co-supervised by Adela Sobotkova and Shawn Ross (in both districts) and by Georgi Nehrizov (in the Kazanlak district), Iliya Iliev and Stefan Bakardzhiev (in the Yambol district). For more detailed information about the project, see www.tundzha.org. 5 Particular thanks are due to Alexey Gotzev, who facilitated the expedition, for his permission and supervision during the data verification process, and to Vyara Petrova of the Archaeological Museum of Professor Mieczysław Domaradzki, Septemvri, for her devoted help and endless enthusiasm during the field works. 6 Weissova 2013, 1047–52. 7 Weissova and Tuslova 2012, 8–11. 8 Special thanks to the Director of the Yambol Historical Museum, Stefan Bakardzhiev, for permission to conduct the survey in the whole macro-region during the 2010 season, and to Todor Vulchev of the Museum for his kind help during data processing and particularly for carrying out the cataloguing of all ground-truthed mounds in the Archeologicheskata Karta na Balgariya (AKB). 9 My thanks to Petra Tuslova, Sona Holickova, Adela Dornakova, Viktoria Chystyakova, Drag- omir Garbov and Emma Jakobsson for their enthusiasm and devoted collaboration during the data verification process. 10 Domaradzki 1988. 11 Marazov 2005. Quantification of Burial Mounds in Yambol District, Ancient Thrace 115 likely on account of the vast number of mounds in Thrace, any quantification of this important archaeological resource is still lacking. The first attempts to quantify the approximate number of mounds within present-day Bulgaria were published by the Shkorpil brothers.12 On the basis of topographical maps from 1878 and 1879, they estimated the burial mounds to exceed 6000 in number,13 with the upper limit of the estimate remaining unknown. Almost a century later, Kitov14 contributed to this topic by making reference to topographical maps of the scale 1:5000. His assessment was based on the results of a surface survey conducted in the Lovech district.15 Kitov pointed out that only about 30% of existing mounds were recorded by cartographers, proffering the observation that mounds of no more than 2–3 m in height or somehow damaged were not usually recorded on these maps.16 However, this assessment lacked more detailed information or specific verification. He further suggested that the relative density of mounds varied according to the elevation of the terrain, basing his statement on his personal observations in addition to the Shkorpil brothers’ analysis of the geographical positioning of mounds.17 The Shkorpils recorded the highest con- centrations of mounds in the lowlands and in hilly areas no higher than 200 m above sea-level, with a decreasing number of mounds at greater elevations and an unconditional absence of mounds in mountainous areas at an altitude of more than 1600 m above sea-level. On the basis of the Shkorpils’ analysis, Kitov posited the number of surviving mounds in Bulgaria to be 19,500. Unfortunately, he did not go further in his analysis and did not record the relative representations of each group of elevations. Finally, Kitov estimated the original number of mounds in Bulgaria to reach 50,000,18 including, as he states, mounds now destroyed: this more than twice exceeds the initial figure based on the geographical model of the Shkorpil brothers. Kitov based this figure on his personal observations of the recent rate of mound decline, but he did not elaborate on the calculations underlying the estimate. Like- wise, he did not relate this result to the earlier figure produced by the geographical model.

12 Shkorpil and Shkorpil 1898. 13 Shkorpil and Shkorpil 1898, 20. 14 Kitov 1993, 42. 15 Kitov 1994, 34–38. 16 Kitov 1993, 42. 17 Shkorpil and Shkorpil 1898, 19–20. 18 Kitov 1993, 43. 116 B. Weissova

A few more studies encompass quantifications of burial mounds, either in Bulgaria as a whole19 or within limited areas.20 The studies are, however, based mainly on registered and excavated mounds, targeting the quantification of different aspects of burial customs and their characteristics within a limited time span,21 not the phenomenon in general. The BUM project, therefore, aims first of all to reassess Kitov’s conclusions through quantified analysis of burial mounds within the three study areas. Eventu- ally, on the basis of the results obtained, the quantified area will be extended to the whole of Bulgaria. This article represents the first attempt of this kind of study, and as such focuses solely on the situation in the Yambol district.

Geographical Characteristics of the Yambol District and Methods Applied Prior the Quantification The study area, the Yambol district, is situated in the south-eastern region of Bulgaria and encompasses a territory of 3355.6 km². It is composed mainly of the plains and uplands of the Middle Tundzha watershed, with elevations ranging between 100 and 150 m above sea-level. The district is one of Bulgaria’s principal centres of agricultural production: the total cultivated area is 77% of the surface.22 The majority of the territory thus falls within the elevation at which burial mounds, according to the Shkorpils’ presumption above, should be most abundant (Fig. 1). The basic prediction of the location of burial mounds for the whole district is based on legacy data recorded on topographical maps of the scale 1:50,000.23 These were published in 1980 using information collected during the 1970s. The BUM project extracted mounds recorded on these maps into one shapefile of points to create the basic dataset for predicting locations of burial mounds. Subsequently, during legacy data verification, the BUM and TRAP projects altogether rectified 34% of these predictions in the terrain. The method of verification was entirely non-destructive and yielded an up-to-date map of existing features. Due to the scale of the map, the projects rectified topographical errors and supplemented each record

19 For an example of studies targeting the whole Bulgaria, see Dimitrova 1997. 20 For examples of studies targeting limited areas, see Nehrizov 1996 (East Rhodope Mountains); Ignatov et al. 1996 (Stara Zagora district). 21 For examples of studies targeting limited areas and specific time frames, see Theodossiev 2000, 25–53 (north-western Bulgaria); Kisyov 2009 (Rhodope Mountains). 22 Official information estimated for the Yambol district to 31.12.1999, see http://www.invest bulgaria.com/Yambol.php. 23 Maps at a scale of 1:50,000 are available online at http://web.uni-plovdiv.bg/vedrin/. Quantification of Burial Mounds in Yambol District, Ancient Thrace 117

Fig. 1: Elevation model derived from ASTER indicating number of burial mounds in the Yambol district, Bulgaria. 118 B. Weissova with detailed information collected in the field.24 The ground-truthed points were used for the quantification of burial mounds within the whole territory of the Yambol district. The macro-regional prediction model based on features extracted from maps of 1:50,000 was further specified by the results of an intensive and systematic surface survey conducted by the TRAP in a micro-region within the study area: Elkhovo municipality. The surveyed area extended to some 30 km². Moreover, 60 km² around this territory was examined through satellite remote sensing25 and subsequent ground control. The detailed coverage of a total of 90 km² enabled the accu- racy and completeness of the topographical maps for archaeological research to be evaluated, not only on the scale of 1:50,000 but also that of 1:5000.26 Inter alia, the results of the study as a whole permitted us to assess the pros and cons of utilising topographical maps in different scales as well as satellite imagery for determining mounds in the territory of Bulgaria.

Results of the Prediction Based on Topographical Maps at 1:50,000 Predictions for the Yambol district based on topographical maps scaled at 1:50,000 yielded 930 points representing possible burial mounds (Fig. 1). Sub- sequently, during verification in the terrain, we visited 318 of these. The selection encompassed samples of diverse land use over the area, though ploughed fields and pastures formed the two most heavily represented groups. In total, 279 of 318 (88%) map-derived locations were confirmed as true positives, i.e. mounds recorded on the map as well as present in the terrain. Four of the 318 points were marked as ‘uncertain’ during ground verification due to their poor preservation. After reconsidering their status, they were added to the total count of confirmed burial mounds, as they were recorded as ‘mounds’ by cartographers four decades ago and only poor preservation had caused their current uncertain status. This increased the total number of confirmed mounds to 283. Two mounds of the total number of 318 were identified as settlement mounds. For statistical purposes these were likewise considered as true positives, i.e. included in the group of confirmed burial mounds. Therefore, the final number of verified mounds in the study is 285 of 318 (90%).

24 Detailed characterisation of the data recorded in the field is covered in Weissova 2013, 1049–50. 25 The Elkhovo multispectral satellite image was captured by Digital Globe’s Quickbird sensor in September 2009 on commission by the TRAP project. 26 Maps at 1:5000 were provided by the History Museum in Yambol. Quantification of Burial Mounds in Yambol District, Ancient Thrace 119

The remaining 33 map-derived points were not located during the ground verification process. Four of these predictions had been eliminated during rescue excavations associated with highway construction across the district,27 and two more were turned into military bunkers during the Cold War. The remaining 27 were either entirely destroyed, or had been erroneously recorded on the topographical map. Regardless of the specific cause, this exercise showed that more than 10% of the map-derived mounds are false positives, i.e. recorded on the map but not present in the terrain. Besides the map-derived points, 157 additional burial mounds were documented during legacy data verification. These false negatives, i.e. burial mounds not recorded on the map but present in the terrain, were almost exclusively located in the vicinity of the map-derived points, creating clusters around them. Therefore, it was also possible to record them during the selective legacy data verification. The number of false negatives raised the total number of existing mounds within the sampled area to 442. In conclusion, from 930 map-derived points, the BUM project and TRAP managed to verify 318 predictions, 285 (90%) of which were ground-truthed as true positives and the remaining 33 (10%) as false positives. On top of this, 157 false negatives were located and recorded during the legacy data verification process, thereby raising the total number of verified mounds to 442. By extending to the entire Yambol district the assumption that 90% of points on the topographical maps represent real mounds, one can expect that the 930 points recorded on the maps will produce some 837 existing burial mounds. Furthermore, if for 285 verified mounds there were 157 additional mounds recorded in the terrain, i.e. for roughly every two ground-truthed mounds there was an additional mound documented in the field at random – in other words, one may expect to find 1.55 mounds in the terrain for every verified mound derived from the topographical map – and assuming that the clustering of mounds remains con- stant throughout the Yambol district, one can predict the total number of burial mounds within the district to exceed 1297. This number comes with the following caveat: the assessment of mounds missing from topographical maps is based on a limited sample from legacy data verification. The sample of false negatives was discovered because these mounds clustered around the ones already recorded on the map and targeted for ground-truthing. Areas marked as empty by cartographers were not visited by the BUM project at all, thus any potential necropoleis there were not ground-truthed. Therefore, this assessment cannot be considered as the final figure without a systematic investigation of the whole area. The number of 1297 features merely indicates the lower limit of burial mounds in the Yambol district.

27 Stoyanov et al. 2010. 120 B. Weissova

Results of the Systematic Surface Survey An additional analysis was conducted in the Elkhovo municipality, in the study area encompassing 90 km² and cutting into the lands of the villages of Borisovo, Boyanovo, Karavelovo, Robovo, Slamino, Stroyno and Zhrebino. One third of this 90 km² was surveyed intensively in a total coverage survey campaign in 2009.28 The remaining 60 km² were examined through satellite remote sensing and ground control. Based on these investigations we now have the total record of 88 mounds present within the examined territory. The prediction based on topographical maps scaled at 1:50,000 yielded 57 points in the territory and, subsequently, the verification team confirmed the presence of 48 in the field. The remaining nine were determined as false positives, thus not present in the terrain. On the other hand, an additional 40 false negatives were registered. These outcomes indicate that the ratio of false positives reaching 10%. False negatives equate 1.83 mounds existing in the terrain per one true positive. In comparison with the prediction previously suggested for Yambol district, this evaluation increased the number of false negatives from 1.55 to 1.83 mounds per each ground-truthed mound. However, the ratio of false positives remained con- stant at 10%. These results confirm the previously stated assumption that the number of mounds predicted solely on the basis of the legacy data verification was underestimated. The quantified model informed by the Elkhovo total survey indicates that the total number of mounds within the district exceeds 1532. The Elkhovo total survey, however, covered only 2.7% of the Yambol district and can hardly be taken as a representative sample for the entirety of it. Interestingly, the elevation of the Elkhovo survey area ranged from 90 to 210 m above sea-level, which falls within that suggested by the Shkorpils as the richest in mounds (see above). As such, the result can be used as the upper limit for the mound density model. Using a combination of topographical maps and surface survey results, the number of mounds within the Yambol district may be estimated to the wide range between 1297 and 1532.

Results of Supplemental Prediction Based on Topographical Maps at 1:5000 Initially, the BUM project intended to utilise maps scaled at 1:5000 to correct and refine the predictions of mound locations in the entire district, but subsequently shelved this idea. Besides the problem with digitising scanned maps of deteriorated quality, the most challenging task was to determine symbols indicating mounds.

28 Ross et al. 2012. Quantification of Burial Mounds in Yambol District, Ancient Thrace 121

Results gained from topographical maps scaled at 1:50,000, together with insights from the systematic surface survey and satellite remote sensing, enabled to determine that not one but seven different symbols used on topographical maps of 1:5000 comport with a mound in reality. Additionally, these symbols represent other features, not only burial mounds. There may be topographical reasons for this hetero- geneity; for archaeological assessment, however, such ambiguity may lead to misin- terpretations. The BUM project therefore preferred to use topographical maps of 1:50,000 as the principal resource and combine them with satellite remote sensing, where possible. However, the 1:5000 topographical maps were used for the area of 90 km² covered by TRAP as a comparative sample to the suggested model. As long as we know the total number of mounds in this area, the ambiguity of symbols does not cause a problem. The legacy data recorded on the map at 1:5000 yielded 77 points in the area and subsequent verification ground-truthed 63 of them. The remaining 14 were false positives. However, 25 false negatives were recorded. Nineteen of 25 false negatives were recorded during the intensive field survey and another six by satellite remote sensing followed by ground control. These results show that there is still a significant number of mounds missing in any cartographical record. Nevertheless, exclusive of the mounds clustered in necropoleis, topographical maps at the scale 1:5000 show only four more mounds than those at 1:50,000. This means that only four mounds would be missed by legacy data verification based on the maps at the latter scale. Provided that the ratio of stand-alone mounds in the area of 90 km² obtains for the entire territory of Yambol district (covering 3355.6 km²), the basic prediction for the whole district based on the 1:50,000 maps should increase the number of features by 149. This predicts 1446 existing mounds for the Yambol district, which falls into the previously estimated range of between 1297 and 1532. These results were compared with Kitov’s statement that the maximum height of mounds not recorded on 1:5000 topographical maps ranges between 2 and 3 m. In the set of 25 false negatives detected on the map at this scale, the arithmetic mean of heights reaches 1.3 m, however the median is 1 m, with the lower hinge at 0.5 m and upper at 1.5 m. The smallest observation of the height is 0.3 m and the largest is 3 m. Only one outlier of 5 m in height was registered. The results show that Kitov’s assertion, based on his observations in the Lovech district,29 applies also to the Yambol territory.

29 Kitov 1993, 42. 122 B. Weissova

Preservation Level of Registered Mounds Mounds suffer, like other ancient monuments, from different types of destruction. Looting,30 agricultural activity,31 erosion and construction works32 are among the most frequent causes. Only a limited number of mounds were not impacted to a great extent by some of these factors. The results of the BUM project show the level of mound preservation and its dependency on the land use. As it appeared during the study, the cultivation of the land strongly affects the rate of decay of the mounds and therefore it is considered in the descriptions as a decisive factor. The preservation levels, expressed in the percentage loss of the embankment, are shown in Table 1:

Level of Preservation and Number of Mounds within Groups.

Preservation Level Rate of Decay (%) Number of Mounds On Cultivated Fields (%)

1 0–20 46 24 2 20–40 102 30 3 40–60 64 30 4 60–80 98 70 5 80–100 121 86

The information is complemented by the number of burial mounds ranked in each preservation group and by the rate of destruction caused by agricultural activities. The preservation levels were determined on the basis of the amount of soil remaining when the mound was visited. For the most part it was a subjective assessment. No exact rule exists to establish the original extent of the embankment, thus we used the ratio of remaining earthwork. The assessments were based on observations in situ and, where possible, on the information gained from denizens and/or literary sources. Before final processing, in order to be consistent for all the documented mounds, I re-evaluated the rating on the basis of reassessing individual field records and the respective photographic documentation. The chart is supplemented by a boxplot (Fig. 2) summarising the preservation levels of mounds located in pasture/forest compared with mounds in cultivated fields. In the case of mounds located in pasture or forest, the mean preservation status is equal to the lower hinge, which is 2, with the upper hinge equating to

30 Renfrew 2000; Brodie and Gill 2003; Weissova and Tuslova 2012, 10–11; Weissova 2013, 1047–48. 31 Kitov 1993, 43. 32 Guichen 2000. Quantification of Burial Mounds in Yambol District, Ancient Thrace 123

Fig. 2: Preservation levels of burial mounds Fig. 3: Number of burial mounds within each located in pasture/forest and in cultivated field. preservation level.

3. In terms of the ratio of missing or somehow disturbed embankment, it ranges between 40 and 60%. Non-outlier observations fall between 1 and 4. No outliers were detected. Mounds in cultivated fields embody, on average, a ratio of decay which is two levels higher than in pasture/forest. The arithmetic mean is equal to the median which equates to 4. The span of non-outlier observations encompasses the whole range from 1 to 5, but the hinge ranges between 3 and 5. In terms of ratio, it falls within 60 to 100% of missing or disturbed embankment. In conclusion, the boxplot shows that most of the mounds located in pasture/ forest are basically still preserved, missing no more than 40% of the embankment, while mounds undergoing cultivation are in a much worse condition, missing 80% of the earthwork on average which is basically equal to an entirely destroyed mound. It is necessary to point out that the results refer to the year 2010. The preservation level changes very rapidly as agriculture and robbery/looting are intense in the Yambol district. Information collected in 2009 (77 mounds) and 2010 (354 mounds) is ranked together, listed from the least to the most destroyed embankments. A summary of the rates of preservation can be seen in a histogram (Fig. 3). This shows the number of verified burials for each preservation status rated from 1 (least damaged) to 5 (most damaged). However, the arithmetic mean of preservation including all the results is not less than 3.4 and median is 4 exactly. This statistic indicates that majority of the mounds in Yambol district have been stripped of 80% of their embankments. The ratio of destruction decreases the probability that the rest of the earthworks still contain valuable 124 B. Weissova finds let alone closed contexts. As long as the financial support to Bulgarian institutions engaged in preserving the cultural heritage is deficient33 and the number of mounds is as high as it currently is, it might be helpful to redirect the endeavour of archaeologists and cultural heritage to selected embankments. The results of the BUM project enable the determination of a reduced number of better-preserved embankments. These mounds were recorded by the project in Preservation Groups 1–3, i.e. missing less than 60% of their earthwork. Some of the mounds ranked in the third group especially require immediate attention. These sites have usually been destroyed by treasure hunters and the disturbance frequently reveals remnants of architectural parts adherent to a larger complex still hidden under the surface. These mounds were recorded ‘in the process of being looted’ and there is high probability that they will fall to robbers within a few years at most.

Detailed Assessments Concerning each Preservation Group Separately The first Preservation Group (Group 1) of perfectly preserved mounds includes 46 burial mounds out of 431. These mounds were either entirely preserved or only partially disturbed, missing less than 20% of the original volume. Most of the mounds (35 mounds) are situated in pastures and covered with dense grass and scrubs. The remainder (11 mounds) are located in ploughed fields. The majority of these mounds exceed 3 m in height, which prevents mechanical disturbance by agricultural machines. Their embankments are relatively well preserved as a result. Moreover, the surface of the well-preserved mounds was usually overgrown with dense vegetation which kept the embankment together. The good visibility of the mounds situated in the middle of ploughed fields or on other private property possibly helped to discourage treasure hunters. Group 2 includes 102 mounds affected by destruction but not exceeding the removal of 40% of the embankment. Regarding land use, a corresponding pattern to the previous group emerges; all of the mounds included in this category and situated in agricultural fields are overgrown with dense vegetation. Like the perfectly preserved mounds of the first group, these mounds subsequently succumb to erosion, intensified by steady ploughing of the surrounding area, even though their height prevents surface ploughing. The third set of mounds (Group 3) includes features where 40-60% of the earthwork has been damaged or removed, a total of 64 from the sample of 431 mounds. Again, as in the second group, 30% are exposed to agricultural activity. The higher ratio of destruction in this case is caused by ploughing of the entire

33 Stancheva 2007. Quantification of Burial Mounds in Yambol District, Ancient Thrace 125 earthwork or by extensive treasure hunting activity. The remaining 60%, located either in pastures or hidden in deep forests, succumbed mainly to looting. Surpris- ingly, the areas overgrown with dense vegetation suffer the most from systematic attention by the treasure-hunting industry: despite difficult access, their hidden position enables unimpeded and persistent looting. Group 4 includes 98 mounds out of 431. The destruction and removal of the embankment reaches as much as 80% of the total original size. Nearly 70% of features in this category were destroyed by intensive ploughing, while 30% succumbed to treasure hunters and the subsequent erosion of the remnants. Group 5, encompassing mounds with less than 20% of the embankment, was recorded in 121 of 431 registered features. The cause of destruction was intensive agricultural work in 86% of cases. These mounds were recognised only through subtle soil marks in combination with very slight terrain waves in the ploughed fields. The remaining 14% were located in pastures; however, most of the fields had been cultivated in the past. Only a few embankments were entirely destroyed by the activities of robbers and by erosion. On the basis of the above results, agricultural activity seem to be the most destructive. However, it is highly probable that the mounds now being destroyed by ploughing had first been looted and thereafter succumbed to the cultivation processes.

Conclusion This paper presents the results of burial mound verification campaigns conducted in Yambol district in 2009 and 2010. The research included comparison of the utility of different resources, from topographical maps of diverse scale to satellite remote sensing and total coverage survey. The use of topographical maps of 1:50,000 for basic prediction, and subsequent completion with the satellite remote sensing appeared to be the most efficient method for detecting burial mounds in the district. Maps at 1:5000 were evaluated as an auxiliary resource. Large-scale maps list more accurate numbers of mounds where small scale maps list a single necropolis. However, they cannot be recommended for primary prediction because of the ambiguous and unreliable use of symbols for mounds that they employ. The number of existing mounds within the district was established to lie within the range of 1297 to 1532. The lower limit results from the verification of predictions derived from topographical maps of 1:50,000; the upper limit from the total coverage survey supplemented by the satellite remote sensing conducted in the micro-region of Elkhovo. 126 B. Weissova

Altogether, 495 points were visited in the terrain during the archaeological campaigns of 2009 and 2010, 431 of them confirmed as burial mounds, and these were further divided according to their state of preservation. Most of the mounds were 80% destroyed. All of the ground-truthed mounds were entered in the official cultural heritage register, the Archaeological Map of Bulgaria (AKB). They have extended the burial mound record in the Yambol district by 431 features. Henceforth, the BUM project aims to continue the verification process of the legacy data and in this way refine the current predictive model.

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Institute for Classical Archaeology Charles University Celetná 20 110 00 Prague I Czech Republic [email protected]