Proceedings of the First International Congress on Construction History, Madrid, 20th-24th January 2003, ed. S. Huerta, Madrid: I. Juan de Herrera, SEdHC, ETSAM, A. E. Benvenuto, COAM, F. Dragados, 2003.

Ornament in Hellenistic architecture: Standardization in construction processes and the birth of the artistic industry. Hypotheses of updating, using CAD/CAM processes

Annalisa di Roma

The main treatises about Classical Architecture and reproduction, to emerge as a model for composition Stereotomy consider the Architectural Orders with and technical principIes. their related elements, as a model for stone The passage fram the unique sculptural model (the construction, in which principals of Composition original) to the serial, simplified model (the copy) and Construction are given as a result of exact praportional correspondence and numerical relations. In the Hellenistic period, the relationship between Geometry and the principal s of construction became very strong, as new rationalistic ideas of beauty as a product of mathematical relations I replaced the aesthetic conception of Art as a product of God's inspiration, codified according to the canons of harmony and rhythm, like Music and Poetry. Rigour in geometrical models is the fundamental characteristic of the main Hellenistic monuments, both in the planning of the Order" and in the planning of ornament too. Geometrical and Construction rules, according to tectonic and stereotomy principals, become essential, given that the elements of architectural decoration of the temple gained meaning in the use of repetition in series and in the device of mutual combination, which followed the passage fram multiplicity to unity. The formal iteration pracess intrinsic to the Hellenistic aesthetic and to the principals of decoration, characterize the whole building structure. In the trilith Figure 1 building, in fact, each element is submitted to the rule Drawing of Temple, archaeo1ogical survey made by George of the series. Each element is conceived of not as Nieman in 1912 for the DAT in Berlin (supplied by the DAT, unique and unrepeatable, but as a characteristic of Deutsche Archaeological Institut, Rame) 766 A. di Roma takes place through a process of stylised methods that author, or by another one, who reproduces the are to be considered fundamental to grand architecture original geometrical model and becomes adept at (see the Temple of Apollo in Didyma) and civil reproducing replicas, creating thus new, unique architecture (the stoa and the Colonnate strips of the objects. Following this logic, the last steps in the Syrian town). sequence is the creation of copies, realized by hand or This paper intends to analyse the artistic by machine, similar to pantographs without any plan. production of the «special piece» and the methods Selecting points from the original, the craftsman and proceedings of serial production in order to develops a kind of mathematical model that becomes discuss the birth of the artistic industry. the basis of the copy. Mathematical models were often very similar to the originals, the difference between the original and the copy being technica!. HELLENISM AND THE BIRTH OF THE ARTISTIC When these copies were produced on a large scale INDUSTRY for the art trade, this kind of technical difference began to be codified using stylised methods. Art coIlection and copy industry

The enlightened rationalism that characterizes Design and building: construction enterprise Hellenistic culture determined the organization of organization and the architect's role scientific and artistic acti vity through the creation of research centres, museums and libraries and operated Works of Classical theory of Architecture were according to the principal s of the division of labour in focused on the aesthetic principal s of Proportions and the intellectual field. Relations between elements of Order, according to Artistic production was employed in the creation of the principals of rhythm and harmony, fine complete Art Collections. Princely and private refinement and perfect execution, which were the collections already existed but only during this period principal topics of such works. is the collection systematically organized according Hellenistic works on architecture speak about to a plan: collections representing the evolution of mechanics and engineering5 showing the change in Greek art, characterized by the search for ancient attitudes to a research in architecture and building. masterpieces, was begun. The search for new aesthetic reference models ceased It is very important to notice that this process, and models were taken directly from cJassical regarding the acquisition of classical art, is achieved tradition. The aims of Hellenistic theory were the also through the birth of artisan workshops engaged invention of new civil and religious building in the production of copies. typologies, conceived to be grand and to give In this way the copyist craftsman compensated for resonance to the expansionist politics of Greece. gaps in the artistic heritage and became involved in a Architectural theory was divided into problems of kind of rhetoric or exercise that provides, first of all, Aesthetics and Practice. Formal decoration became for an enrichment of the formal repertory and ecJectic with a contemporary use of subjects secondarily increases the spread of new technical consolidated and codified in the Classical and Ionian knowledge in proto-industrial serial production and periods, and new subjects taken from Asiatic process.3 traditions (for example decoration in Didymaion is In the passage from the original artistic object to characterized by the use of actical profiles in the series of replicas and copies, it is possible to mouldings and samic subjects in the decoration). On recognize the beginnings of standardization in the technical side, more rationalized processes in production methods: the geometrical model and the stonework took place, based on the specialization of Original, numerical model and the Copy. work phases and on the creation of an artisan The principal characteristic of the artistic object, dimension in serial production. the special unique piece, is that only the author who This kind of specialized organization was based on conceived it masters the geometrical mode!. The the use of different workers for the same building and original is followed by replicas4 made by the same for each carved stone, the aim of skilled work was Ornament in Hellenistic architecture 767 speed of execution and a good finish. However, in the codified position of Order. In the last phase, the Greece the reunification of different areas in a single, skilled craftsmen carved this element following the large enterprise was never realized. ornament design made by the architect of the temple, The Temple of Apollo at Didyma is an example of copying a model for capitalsJor the column entasys, the grand Hellenistic Ionian building in which many for the moulding profiles and the architectural different classes of worker were employed for a very decoration they utilized a guide-plane, as well as with long time (the construction started around 334 B.C. strips sculpted on the blocks of the wall of the cellar and went on slowly for 600 years -it was never and the stylobade. These are the blueprints (fig 2) for finally finished) creating a structure made of 108 the temple discovered by Lothar Haselberger in columns. Greek workers were used at the beginning 1979.7 and Roman workers at the end. According to The architects Daphnis of Mileto and Paionios of H. Lauter (1986) workers assigned to the Didymeion Ephesus designed Didymeon. In the Greek practise of were a sort of stately slave.6 There were four main planning the construction phases of the temple, there categories of worker: the latomai assigned to the was an architekon and a hyparchitekton. The first was quarry phases, the leukorgoi who transported the essential to the life of the building, he was familiar handmade stone block s from the quarry to the Temple with the complete architectural plan, directly yard, the egemon, a supervisor who directed the involved in part of it and directing the work in activities of the other two classes of worker, and progress. In the building yard he was responsible for finally the skilled craftsmen, responsible for the yard the technical direction of all activities and, phase. The Latomai quarried stone blocks congruent completely independently, could plan and approve in dimension to the planned architectonic elements small interventions in the immediate building area. and gave the essential geometrical shape to the stone. The hyparchitekton, on the other hand, was The Leukorgoi transferred the pre-manufactured committed to the direct supervision of each individual blocks to the temple site and then began the process block production. In this kind of organization seems of shaping and refinishing them (anathyrosis). The to be very clear the strong relationship between architectural stone element was situated according to design and construction.

Morphological development of elements pertaining to the Orders through the process of standardization

In the wake of evolution in building types and large scale production processes, elements pertaining to the classical orders have undergone a series of noticeable changes regarding formal details as well as involving substantial modifications to the morphological characteristics of blocks, both due to the diminishment of the original structural role. These changes effect, above all, elements of moulding and entablature. What initially might appear as a new form or as an added form to the ornamentation, is, in reality, evidence of how the tectonic quality of building elements have lost their original strength. With regard to moulding, the most substantial variations can be seen in the Doric triglyphon, an Figure 2 eminently tectonic element in which it is possible to Blueprints far the temple discavered by Lathar Haselberger witness a noticeable loss of the sense of alternation in 1979 (from Haselberger, 1985) between metope and triglyph. The metope, which 768 A. di Roma originally represented an interruption in the pattern of According to the archaeological tradition, they are the wooden beams, increases in size, giving space to represented by two-dimensional sections, representing the secondary plastic. This expedient was aimed at combinations of circular arcs filled to create the creating a plastic effect of chiaroscuro, eliminating listello, cavetto, gola rovescia and so on. for the most part the structural differences between From an architectural point of view they are metope and triglyph; the represented objects, in this parallel-piped stone blocks, characterized by three way, have a structural role, upsetting the tectonic planar and orthogonal faces and one sculpted surface, sense. extruded to cast a linear or a curved path. The manipulation of building elements such as Indeed, each face of the block is precisely refined: entablature (or frontaJs) reveals not only a clear the contact side of the block is scored to create the variation of the structural role but the whole anathyrosis. This kind of finishing allows for the traditional system, based on a clear relationship perfect assembling of the block and, most between single blocks and the organic structure, is importantly, functions as a device to pass from the called into question. Even blocks used in the cornice single block to the organic structure of the buiJding as reveal a progressive deconstruction of the original a whole (from the unique to the multiple). monolithic aspect. 8 The cornice becomes an According 10 Karl Bottier (10) this kind of assemblage of movable pieces, attachabJe and morphological envelope corresponds to the Tectonic detached. needs. He says that Tectonic referring to Greek In this way, compositional processes are born architecture means exact and congruent functions of based on the concept of series repetition and to which the members into the arder' s system according to completely new formal qualities are associated, with their structural roleo new proportional relationships between the various In the Doric arder, ornament represents the stone elements. evolution of the archaic wood temple and mouldings In general, these morphological and tectonic were scantily decorated. The lonic tradition allowed changes are most evident in the reduction in thickness for more decorative themes, often inspired by natural of the blocks, an aspect that responds directly to the subjects or of a textile derivation. Leaves, weavings economic obligations imposed by primary materials, and meanderings are the most characteristic and to the increase in production speed and assembly decorative themes from the Archaic period to necessary in the construction of civic buildings, for Hellenism. Those natural or fictile subjects were example the stoa and the colonnades of commercial processed by geometrical and stylised methods to Syrian cities. become repeatable in succession, in the same moulding or the same building and beyond. Decoration was applied to painted or sculpted THE ORNAMENT IN ARCHITECTURE moulding profiles.

Mouldings and decoration Standardization in Hellenistic ornament production The analysis of architectural ornament begins with the distinction between mouldings, pertaining to the Stone architectural element production has always architectural field and decoration, pertaining to been dominated by a series of rationalized figurative one. During the archaic age the association proceedings that are to be intended as a series of between decoration and profile was rigidly operations organized to create a finished product, and controlled,9 while Hellenistic culture was open to new methods that are models for specific action. combinations. Indeed, during the Hellenist period an The first operative stages in ancient stone enrichment of the formal repertory, made up of working, followed standardized procedures and different styles and traditions, takes place. methods in the quarry itself and included quarrying Mouldings are serial architectonic elements set in a and squaring These two operations were regulated by Greek arder and their sequence and combination standardized measures congruent with the generates the language of stone trilythic architecture. architectural element to be realized. The stone blocks Ornament in Hellenistic architecture 769 are first worked in the quarry where they are squared. At Didyma, general information about the shape of The quarrying of the stone was performed following the moulding sections, the size of the enthasis of the precise economic need of limiting off-cuts. The columns etc., is still visible on the cell walls and on stone blocks were thus quarried according to the the stylobate blocks because, as this Temple was required size and type of architectural element to be never finished, such graffiti, which represents the fashioned. The second operation performed in the Greek working methods, was never smoothed off or quarry was the squaring of the block, a task cancelled. performed with great care as an ill-squared or The mouldings were sculpted with stylised imperfect face could compromise successive work decorative sketches, which functioned as a guide for phases. The next phase includes the rough-shaping of the artisans who decorated the stone. Following this the block, using dime and huges and subbias, before method of directing work by architectural sculptors, the successive, final finishing. The process of the final surface is sculpted before them. The ornamentation is only partly realized before the sculptors were required, above all, to produce a block is put into position, or until the process of faithful copy of the original. Finishing of block s with moulding is begun. (Tav. 1) fiat surfaces was performed once the block had been These initial work phases saw at least two classes positioned in the wall. The sculpting of contact of specialized workmen working on the same block surfaces (anthyrosis) had to be performed with great and it is probable that different workmen worked at care as they were the principal elements of formal the same task. In such cases, it was essential that the juncture between surfaces that had to be perfectly tlat work proceeded according to standardized methods, and those which continued the decoration. Evidently, given that the various sculptors involved worked the fa<;ade had to be sculpted once all the blocks were towards finishing a single block. Mouldings or in position. capital s for example had to reveal the same pattern on The development of the idea and its development different sides. before and during the work phases, constitute the technique of stone working.

Decorative patterns: planar curve to surface (T A V .11, III)

Decoration could be developed following a process of either direct or indirect designo In the first case the artistic component of the sculptor, who develops his own design directly on the stone, prevails. This methodology is contrary to the principIes of standardization, and its the fina] product is a «special piece», that is difficult to produce and reproduce in faithful copies for the team of stone masons. Indirect design implies characteristics of repetition, and the decorative pattern corresponds to precise geometrical rules, which prevail over the purely figurative components. The method of direct design in Hellenistic architecture was predominantly used in the Figure 3 production of «special pieces» to be inserted into Synoptic plate 1, work phases from the squaring of the block bui1dings as representative of a certain monumental to the redesigning of the moulding's surfaces. Drawing by spirit. The indirect method was more commonly used the author (September 2002) in the serial production. 770 A. di Roma

Moulding's surfaces are always being deveJopable In the ancient methods this theory was applied in in planar surfaces: this means that it is possible to the determination of stylised guide line sculpted in the study the decorative patterns in their planar first work of the row block. configuration, and to project the planar curve to surfaces. In this way starting from the original configuration of the decoration is possible to achieve different kinds of 3D patterns, according to the development surfaces, both linear and/or generated by revolution, on which it had been projected. In this light the Decoration design could be divided in two main phases:

- The first regard definition of two-dimensional pattern. - The second pertain to the study of the three- dimensional moulding's surfaces and their related planar development.

The two-dimensional decoration is proportioned to the planar envelop of moulding's surface and then projected on the three-dimensional surface. This method is based on the geometricaJ principIe of congruence between surfaces and planar curve developed. Figure 5 Synoptic plate III Apol1o Temple at Didyma: development of the planar decoration pattern on the entablature moulding's surfaces. Drawing by the author (September 2002)

STANDARDIZATION IN CAD-CAM PROCESSING.

Cad/cam methods and processes

The hypothesis of updating stone architectural ornament design and production processes is based on the possibility of applying modern stone cutting technologies through the use of cad-cam. The aim of such a research hypothesis is the development of contemporary architectural forms to be used mainly in restoration sites. Electronic Design replicas, referred to ancient Orders and Ornaments, allowed us to comprehend the Figure 4 complexity of classical geometrical models and Synoptic plate 11, Apol1o Temple at Didyma: development of the planar pattern to the curved surfaces of the astragal, technical knowledge in sketching and finishing and stylised deeorative sketehes sculptured on the surfaces. moulding's surfaces. Drawing by the author (September Starting from the study of the single special 2002) element, the reflection led to the methods that are to Omament in Hellenistic architecture 771

be consider valid for replicas and copies' serial two main categories: those which use their forrn to production. II reproduce predisposed form and those with a cylindrical On the basis 01' the archaeological survey's data, or spherical form. The first kind 01' tool is generally used the Cad design allowed us to reproduce the original to make contours and incisions, the second type in rough geometric model and to make a virtual three- shaping and finishing. The variables to be decided on in dimensional replica, that could be considered likely choosing tools include rotation speed and progress identical to the original. speed, depending on the characteristics 01' the stone and Cam processing concerns the planning 01' work- the shape to be achieved. phases in making replicas. The last steps in a CAM project is the generation 01' The first step is to import cad project files (dwg, CN filesl2 made by a cam software. This file contains iges and so on) and then to choose the number and the all the information about labour, finishing and tools kind 01'processes, the number and the kind 01'tools. changes. Work cycles are divided into two main categories, rough-shaping and finishing. These two phases 01' work in progress correspond to a growing approach to Sketched and tinished surfaces in the andent age the form, from the parallelpiped block to the final and in Cad-Cam production ornamental element. The second step is the tools' choice, the number and The tools choice and the techniques of rough-shaping kind 01' which depend on row-block dimension, final and finishing are important for any research project element morphology and the kind 01' sketching and that intends to recover the expressive nature of stone, surface finishing. In the tools repertory we distinguished since certain plastic outcomes of the period are to be

I

Figure 6 Synoptic plate IV Apollo Temple at Didyma: the 3D virtual model of the naikos wall base's moulding, and CNC Work phases for the prototype's realization (Laboratorio Cad-cam, Dipartimento lCAR, Scienze dell'Ingegneria Civile e dell' Architettura, Politecnico di Bari, June 2002) 772 A. di Roma

evaluated as the result of the tools which were used NOTES for the percussion. The study of the artisan ornamental techniques used l. The philosopher Platone in the Res Publica expresses the conception of beauty as a strong relationship in Hellenistic building sites permits a comparison of between geometrical shapes and mathematical the similarities and differences between a manual proportion. production system and a mechanical system using 2. Doric Order was exactly ruled in the VI B.e.c. and only numerical controlled machines. few changes in decoration and proportion appear during In ancient building sites the constructions of the following centuries. The architects of the Asia finished elements necessitated a series of work phases Minor codified ionical Order later in IV B.e. c. (often performed by different specialists) analogous 3. «Accanto alle botteghe dei ceramisti, che in parte with mechanized systems in which the number ofjobs lavorano gia con sistemi industriali, comincia la to do depended on the nature ofthe object to construct produzioni su vasta scala di copie dei capolavori della scu1tura. Senza dubbio le stesse botteghe e le stesse and on the type of ornament. persone producevano anche opere original i ma e A decorated surface would be subject to at least naturale che gli scu1tori, esercitando quel mestiere di three work phases, which would increase in relation to copisti, si lasciassero facilmente sedurre dal puro the morphological characteristics and to the number virtuosismo stilistico». (Hauser, 1986) and type of tools necessary to the stone-cutting. In the 4. Kugler (1972) gives a precisely distinction between ancient period the production of different blocks was original object and copies according with aesthetics' often the responsibility of various workers and the principies. The formal class is expressed «da oggetti result was a slight difference between the pieces. The primi o da cose dotate di grande potenza generati va, production of a series of elements entirely produced quali ad esempio il Partendone [ . . . ]. Anche se parte with mechanical processes, on the contrary, del loro splendore e andato perduto col tempo, la loro qualita di oggetti primi resta indiscutibile». guarantees absolute similarity.'4 5. Vitruvio dedicates the X'h book of the Ten book on In the ancient period the first work phase after the Arehiteeture, to the construction of machine for the squaring of the block was the redesigning of the construction. orthogonal surface of the moulding. The pattern was 6. Building's enterprises were generally managed by accomplished using dime and boring tools. The dime private organization. were generally made in wood and appear as the 7. Lothar Haselberger (1985) discovered in October '79 negative of the mouldings, they permitted the control many etched line on some of walls 01'the Temple. Then of the required shape during the sculpting process. he realized that those strips should have been the The circulation of templates and pattern cards construction plans for the temple of Apollo at Didyma. throughout the building sites was associated with the 8. Trevor Hodge (1960) makes an interesting comparison mobility of artisans and allowed for the rapid between the cornice's blocks of the main temple from the Archaic to Hellenistic age. execution of similar elements. Only in the final 9. According to Giorgio Rocco (1994), Greeks inherited surface finishing phase were abrasive tools used. from Egyptian Architecture the two main moulding: the The mechanized processes employed by eavetto or gola egizia and the semieerehio. Hellenic computerized numerically controlled machines use culture taken this two forms and developed five new milis and rotating drums which need materials with formo The semieerehio was used in his linear and different characteristics to those required by scraping original form and became the toro for the columns' off tools. Certain processes (including «bush bases. The be eco di civitta and the gola rovescia were hammering», which is typical of the surfaces between typically used in the Doric Order and gola roveseiu and the blocks and the drums) do not appear to be the ovoli in lonical Order. reproducible with off-cut techniques. Thus it is 10. Karl Botticher, neoclassic architect and architecture's theorist. necessary to establish a priori both the type of tools 11. Prof. D' Amato (2002) speaks about the replica of the necessary to create the desired effect and the right type 9A Doric Capital of the Temple of Apollo Epicurio at of operation (wholly mechanical, partially manual Bassai. He makes a comparison between an artistic etc.). This problem is more comp1ex in the study of replica and an architectural one. decorative pieces, in which the finished product 12. A CN file is written in an ISO-normalized format and reveals both intaglio and, sometimes, fretwork.13 adapted to characteristic of the Numeric Controller Omament in Hellenistic architecture 773

Machine by the CAM-software. The file elaborated by Archaic and Classical Periods, British School of the author was processes by the cam software of the Archaeology at Athens, volume n.3 , London: Thames Easy lI CNC machining centre of the Laboratorio Cad- and Hudson. cam at the Politecnico di Bari for the realization of a first Adam, S. 1966. Ancient Greek architects at work, problems moulding prototype with the imbricate lea ves, presented of structure and design, Oxbow Books. during the Study Seminar «ARCHITETTURA E Coulton. J. J. 1970. Ancient Greek architect sat work, STEREOTOMIA: TRADIZIONE E INNOV AZIONE. problems of structure and design, Oxbow Books. Giomata di studi sull' Architettura in Pietra da Taglio», D' Amato Guerrieri, C. 2002. La replica del capitello 9° del 3-4 June 2002). Tempio di Apollo Epicureo a Bassai, in Area n° 62. 13. The paper summarises some aspects of the on-going Hodge, Trevor. 1960. The Woodwork of greek roOf5, Doctorate dissertation the author is carrying out at the Cambridge university press, Londra Politecnico di Bari, and titled La decorazione Ginouves Rene'. Roland Martin. 1985. Dictionnaire Architettonica ellenistica: dal pezzo singolo artigianale méthodique de l' architecture grecque et romaine. alla produzione in serie. Tutor: Prof. Claudio D' Amato Matériaux, techniques de costrution, techniques et formes Guerrieri, Politecnico di Bari, PhD Course in du décor, Vol. 1 Ecole Franyaise d' Athenes, Ecole Progettazione Architettonica per i Paesi del Mediterraneo, franyaise de Rome. cic10 XVI. Ginouves. Rene'. 1992. Dictionnaire méthodique de l' architecture grecque et romaine, Eléments constructifs : supports, couvertures, aménagements intérieurs. Vol. TI REFERENCE LIST Ecole Franyaise d' Athenes, Ecole franyaise de Rome. Orlandos, A. K. 1966-68. Les matériaux de construction et Choisy, Auguste. 1987. Histoire de l'architecture, Parigi : la technique architecturale des anciennes Grecs, travaux Slatkine Reprints, Ginevra. et Mémoires XVI. Paris: Befar. Charbonneaux, Jean; Roland, Martin and Villard, Francois. 1971. La Grecia Ellenistica (330-50 a.c.). Milano: Rizzoli Editore. History of the Art's critics Dinsmoor, W. Bell. 1973. The architecture of ancient Greece. New York: Biblio and Tannen. Hauser. Amold. 1993. Storia sociale dell'arte, trad. it. a cura Fyfe, Theodor. 1936. Hellenistic Architecture. Cambridge: di Anna Bovero. Torino: Piccola Biblioteca Einaudi. Cambridge University Press. Kubler, George. 1972. La forma del tempo. Torino: Piccola Lauter, Hans. 1986. Die Architektur des Hellenismus. biblioteca Einaudi. Darmstadt: Wiessenchaftliche Buchgesellschaft. Italian Riegel, Alois. 1959. Arte Tardoromana. Torino: Einaudi. ed 1999. L'architettura dell'ellenismo, italian translation Owen, Jones. 1856. The grammar of ornament, London. by Amalia Faustoferri, Milano: Longanesi. Venturi, Lionello. 1964. Storia della critica d'arte, piccola Lawrence, A. W. 1990. GreekArchitecture, Vth, Yale: Yale biblioteca Einaudi, Milano university press. Rosa W. Denman. Semper Gottfried. 1992. Lo Stile, a cura Rocco, Giogo. 1994. Guida alla lettura degli ardini di A.R. Burelli, C. Cresti, B. Gravagnuolo, F. Tentori, architettonici antichi: il dorico. Napoli: Liguori editore. Prefazione di V. Gregotti, Editori Laterza. Roland, Martin. 1998. Architettura Greca, in Storia Specialized readings about The Temple of Apollo at universal e dell' architettura. Milano: Electa Didyma. Webster, T. B. L. 1967. Ellenismo. Milano: 11Saggiatore Akurga1, Ekrem. 1983. Ancient civilization and ruins of Turkey, lstanbul. Fonterose,1. 1988. Apollo's oracle, cult and companions. More technical readings Berkley. Haselberger, Lothar. 1985. The construction Plans for the A.A.V.V. 2000. L'artisanat en Grece ancienne : Les temple of Apollo at Didyma, Scientific American, vol. productions, les diffusions , édite da Francine Blonde e 253 n° 6. Arthur Muller, Travaux et Recherches, Paris. Turchelt, K. 1986. Fragen zum Naiskos von Didyma. Adam, S. 1966. The Technique of Greek Sculpture in the Istanbul.