Το εξάγωνο στη βυζαντινή αρχιτεκτονική

Abstract

The hexagon is a regular geometrical figure, with six sides and six angles that are equal with one another and with 120o degrees each. It is carved based on the circle, with whom it shares a common spoke, and thus it is inscribed in it better and easier than in any other geometrical figure. One of its main characteristics that influences its application on architecture is the disparity of its vertical axes -the middle and the diagonal- that does not allow its inscription in a square but only in a rectangle. As a regular figure it can be found in nature, in beehives and it is in this very shape that it is traced as a decorative theme in the archaic period. The hexagon in monumental architecture is applied on central plan buildings already from Antiquity and it has always been related to the circle, which is the predominant figure. It appears in a clear, autonomous form in the Imperial era in buildings and interior places. In christian architecture it has been widely applied not only in big buildings but in smaller, functional constructions of religious character (baptismal fonts, pulpits, ciboria, phialae). The historical and geographical expansion of the hexagon is characterised more by concentrations of similar examples rather than interspersed and isolated ones: early christian baptismal fonts in Istria-Dalmatia, Rome and North Africa, early christian pulpits in Dalmatia and Palestine, late antiquity buildings in Rome, Thessaloniki and Constantinople, mid-byzantine buildings in Dalmatia, Georgia, Armenia and Transylvania, semi-hexagonal apses in churches of the Helladic school, “hexagonal” domed churches near Preslava. The isolated hexagonal examples, in many occasions, appear to be in short geographical or/and chronological distance from some of the above mentioned structures. The “grouping” of the applications of the hexagon has much to do with a relation between the original pattern and the copies that can be traced, in most of the cases anyway. This relation is interpreted: a. by its singularities and its “disadvantages” in shape during its application in architecture that make it less or semi-popular and b. by its big and special symbolic and doctrinal importance that is taken advantage of in specific cases. Chronologically speaking, the majority of hexagonal applications are traced back in the early christian era and, within this amount, the biggest part are the hexagonal baptismal fonts and not the applications of monumental architecture. It seems that the singularities in its figure, on one hand, have limited its application and, on the other, they have made the bipolar relation between the original pattern and the copies stronger. The hexagon definitely does not belong in the most popular and widespread figures of central planned buildings; the circle and the octagon prevail, maybe even the cross (combination of two rectangles.) Despite the easy way of its inscription, as a figure that derives from the circle, it has two main disadvantages: a disparity of axes and a relatively large size in the sides. The disparity of axes is a disadvantage of figure in combination with the prerequisites for door opening. Doors and windows were opened only in sides and not in angles, for static reasons. The main entrance of a building defines its axis too; and since it is opened in the middle of the side obligatorily, the main axis of the hexagonal building becomes its middle axis instantly, the smallest of the two axes of the figure (the other one is the diagonal one). Thus, the building is, on one hand, central planned but it has, on the other, reversed naved form (its width being bigger than its length). This is probably the reason why there cannot be located any hexagonal buildings inscribed in a free four sided while, on the contrary, there can be found many octagonal buildings inscribed in a square. A unique case of the application of the hexagon is the structure of Agia Sophia in Constantinople. With the separation of the hexagon in two halves and the insertion of the domed core in them, inscribed in a square, the now complex figure acquires a sense of being naved, whereas the necessary four conches in the angles of the theoretical inscribed rectangle are rather small by comparison. Furthermore, it is the unique perhaps case of the application of the hexagon in the structure of a building of a very large scale. The degree of dependence of the design of Agia Sophia on the already existing Agia Efimia can not be determined, it is though an assumption that can not be eliminated. An extreme case of relation between original pattern-copies is probably related with Agia Sophia , at least from the aspect of the distance in time, the application of the hexagon in eight very important muslim shrines, all being Sinan’s constructions. The special symbolic value of figure is placed among the general frame of symbolism of central planned buildings from the moment of their appearance till modern era. Pagan, Greek and Roman central planned buildings combined, in the same structure, different from one another uses and, therefore, different symbolisms too. In that period the religious uses and the relevant symbolisms go together with more secular ones, political in particular. Pagan central planned are connected either with the state and religious characteristics of Ancient Greece or with the civic roman culture of the centuries of the Empire that acquires a more and more concentrated civic character; Christian hexagons have, as the rest of the central planned of their era, strong symbolisms, mainly religious ones: the most important are the connection of death with christening and the strengthening of the orthodox, triadic doctrine in areas that were plagued by religious sects (Istria-Dalmatia, Northern Africa). The hexagonal baptismal fonts combine, in many cases, more symbolic figures: hexagon, octagon, four-light, per two or per three or they are placed in the centre of octagonal baptismal fonts. Medieval six-conch buildings have, in many cases, a burial character, but a there is a secular symbolism that recurs: many of them are capellae regiae or they praise and, in several ways, they strengthen the power of secular leaders. The total absence of this type from the territories of Byzantium during the middle and later byzantine era and its presence in regional states, which had a client-like relation, states a rather provincial anachronism, that takes advantage of intact types of the past -translated into regional dialects in more or less creative way- to bring back the lost prestige and to work as a conjunction to the most powerful state of the region, the Eastern Roman. It is doubtful whether the only two byzantine “hexagonal” churches, that bring back memories from the early christian past and create though a new type of building, can be considered monuments with powerful, secular at least, symbolisms. Examples of monumental buildings and furniture construction in an hexagon can be found roughly: a. in a composition with the circle as a subordinate figure. b. in a composition with the circle as an equal or main figure. c. in a composition with itself or as a product (twelve-sided). d. in a composition with a four-sided, simple rectangle or a crossing of rectangles/cross. e. in a composition with more figures such as the circle and rectangle, octagon and rectangle, octagon and square. Typologically hexagonal buildings can be distinguished in the following categories: a. free hexagons, few in numbers and predominantly having wooden roofs. b. conched hexagons, free and inscribed. Conched hexagons all have vaults. c. double shelled buildings, a group with an equally limited number of examples, where both types of cover can be found. A special category of application of the hexagon in monumental architecture are the semi-hexagonal apses. Even though they can be found in all eras, they become especially popular in the monuments of Helladic school. Furniture follows the typology of the buildings. With the exception of baptismal fonts, that can display some particularly complex structures, the rest follow the free hexagonal figure. Hexagonal structures, even though they are not the most widespread like octagonal or circular, they are not rare like the central planned constructions with an odd number of sides. They can be found in all eras, late antiquity and middle ages and in all former roman Europe, even beyond its borders. Their construction suggests special reasons, related with design and ideology. In late antiquity they demonstrate a sophisticated design and they can be found in big, urban centres, whereas in Middle Ages they can be traced in regional areas, outside of Byzantium, as a conscious anachronism. When they are found, even in the gothic period of art, they copy oldchristian, architectural or ideological, original patterns. This relative spread during medieval times demonstrates that the roads of communication between the roman past and the present of christian states, old and new ones, even between “orthodox” Byzantium and “catholic” West were not closed.