Editing Byzantine architecture (section)

==Structural evolution==
[[File:Hagia sophia mathematische Konstruktion.jpg|thumb|The geometric conception of the Hagia Sophia is based on mathematical formulas of Heron of Alexandria. It avoids use of irrational numbers for square diagonals and circle circumferences and contrieves thus a highly elaborated mathematical space]]
As early as the building of [[Constantine the Great|Constantine's]] churches in [[Palestine (region)|Palestine]] there were two chief types of plan in use: the [[basilica]]n, or axial, type, represented by the basilica at the [[Holy Sepulchre]], and the circular, or central, type, represented by [[Domus Aurea (Antioch)|the great octagonal church]] once at [[Antioch]]. 
[[Image:StGeorgeRotundaSofia.JPG|thumb|left|The St. George Rotunda; some remains of Serdica can be seen in the foreground]]
Those of the latter type we must suppose were nearly always [[Vault (architecture)|vaulted]], for a central [[dome]] would seem to furnish their very purpose. The central space was sometimes surrounded by a very thick wall, in which deep recesses, to the interior, were formed, as at [[Church of St. George, Sofia]], built by the [[Ancient Rome|Romans]] in the 4th century as a cylindrical domed structure built on a square base, and the noble [[Arch of Galerius and Rotunda#Rotunda of Galerius|Church of Saint George]], [[Thessaloniki]] (5th century), or by a vaulted aisle, as at [[Santa Costanza]], Rome (4th century); or annexes were thrown out from the central space in such a way as to form a cross, in which these additions helped to counterpoise the central vault, as at the [[Mausoleum of Galla Placidia]], [[Ravenna]] (5th century). The [[Church of the Holy Apostles|Holy Apostles, Constantinople]] was off this type. Vaults appear to have been early applied to the basilican type of plan; for instance, at [[Hagia Irene]], [[Constantinople]] (6th century), the long body of the church is covered by two domes.

[[File:Hagia Sophia Interior Dome.jpg|thumb|upright|Interior of the [[Hagia Sophia]] under renovation, showing many features of the grandest Byzantine architecture.]]

At [[Little Hagia Sophia|Saint Sergius]], Constantinople, and San Vitale, Ravenna, churches of the central type, the space under the dome was enlarged by having apsidal additions made to the octagon. Finally, at [[Hagia Sophia]] (6th century) a combination was made which is perhaps the most remarkable piece of planning ever contrived. A central space of 100&nbsp;ft (30 m) square is increased to 200&nbsp;ft (60 m) in length by adding two [[hemicycle]]s to it to the east and the west; these are again extended by pushing out three minor apses eastward, and two others, one on either side of a straight extension, to the west. This unbroken area, about 260&nbsp;ft (80 m) long, the larger part of which is over 100&nbsp;ft (30 m) wide, is entirely covered by a system of domical surfaces. Above the [[conch]]s of the small [[apse]]s rise the two great [[semi-dome]]s which cover the hemicycles, and between these bursts out the vast dome over the central square. On the two sides, to the north and south of the dome, it is supported by vaulted aisles in two stories which bring the exterior form to a general square.

[[File:Hagia Eirene Constantinople 2007.jpg|thumb|left|upright|The apse of the church with cross at [[Hagia Irene]]. Nearly all the decorative surfaces in the church have been lost.]]

At the Holy Apostles (6th century) five domes were applied to a cruciform plan; the central dome was the highest. After the 6th century there were no churches built which in any way competed in scale with these great works of Justinian, and the plans more or less tended to approximate to one type. The central area covered by the dome was included in a considerably larger square, of which the four divisions, to the east, west, north and south, were carried up higher in the vaulting and roof system than the four corners, forming in this way a sort of [[nave]] and [[transept]]s. Sometimes the central space was square, sometimes octagonal, or at least there were eight piers supporting the dome instead of four, and the nave and transepts were narrower in proportion.

If we draw a square and divide each side into three so that the middle parts are greater than the others, and then divide the area into nine from these points, we approximate to the typical setting out of a plan of this time. Now add three apses on the east side opening from the three divisions, and opposite to the west put a narrow entrance porch running right across the front. Still in front put a square court. The court is the [[Atrium (architecture)|atrium]] and usually has a [[fountain]] in the middle under a [[canopy (building)|canopy]] resting on pillars. The entrance porch is the ''[[narthex]]''. Directly under the center of the dome is the ''[[Ambon (liturgy)|ambo]]'', from which the Scriptures were proclaimed, and beneath the ambo at floor level was the place for the choir of singers. Across the eastern side of the central square was a screen which divided off the ''bema'', where the altar was situated, from the body of the church; this screen, bearing images, is the ''[[iconostasis]]''. The [[altar]] was protected by a canopy or ''[[Ciborium (architecture)|ciborium]]'' resting on pillars. Rows of rising seats around the curve of the apse with the [[patriarch]]'s throne at the middle eastern point formed the synthronon. The two smaller compartments and apses at the sides of the bema were sacristies, the ''[[diaconicon]]'' and ''[[prothesis (liturgy)|prothesis]]''. The ambo and bema were connected by the ''solea'', a raised walkway enclosed by a railing or low wall.

The continuous influence from the East is widely shown in the fashion of decorating external [[brick]] walls of churches built about the 12th century, in which bricks roughly carved into form are set up so as to make bands of ornamentation which it is quite clear are imitated from Cufic writing. This fashion was associated with the disposition of the exterior brick and stone work generally into many varieties of pattern, zig-zags, key-patterns etc.; and, as similar decoration is found in many Persian buildings, it is probable that this custom also was derived from the East. The domes and vaults to the exterior were covered with [[lead]] or with tiling of regional variety. The window and door frames were of [[marble]]. The interior surfaces were adorned all over by [[mosaic]]s or [[fresco]]es in the higher parts of the edifice, and below with incrustations of marble slabs, which were frequently of very beautiful varieties, and disposed so that, although in one surface, the coloring formed a series of large panels. The better marbles were [[bookmatched|opened out]] so that the two surfaces produced by the division formed a symmetrical pattern.