A common theme in the history of Byzantium of this period is the attempt to ban the veneration of icons (the representation of saintly or divine personages). This Iconoclastic Controversy raged for a century, from the time Iconoclasm became an imperial policy under Leo III in 730 until icon veneration was officially proclaimed as Orthodox belief in 843. In spite of this controversy, and the reduced prosperity of the state during this period, churches continued to be built, including the church of the Assumption at Nicaea (now İznik, Turkey) and Ayía Sofía at Thessalonica (Thessaloníki). The emperors were not necessarily opposed to all building and art, however. It is known from texts that Theophilus (829–842) was responsible for numerous additions to the Great Palace.

The middle Byzantine period (843–1204)

The most understanding of the emperors in the years immediately succeeding Iconoclasm was Basil I (867–886). Like many of his predecessors, he built in the area of the Great Palace, his most interesting contributions being two churches, the New Church and the church of the Theotokos of the Pharos. These set a fashion in church building and decoration that was to exercise an influence for many centuries. Neither survives, but something is known of them from written descriptions; it would seem that both were typical of what was to be the mid-Byzantine style. Broadly speaking, the churches of this age conform to a single type, usually termed the cross-in-square. It is made up of three aisles, each one terminating in an apsidal chapel at the east, with a transverse nave, known as the exonarthex, at the west. Invariably, there was a dome over the central aisle, supported on four columns, with four vaults radiating from it to roof the central aisle to the west, the sanctuary to the east, and the central portions of the side aisles to the north and south. These vaults rose above the roofs of the other portions of the building, so that the church was cruciform at roof level. Excluding the exonarthex, the churches were usually almost as broad as they were long, making the basic plan virtually a square. Occasionally, additional columns were used to extend the nave westward, producing a type known as the domed basilica; sometimes the walls separating the eastern ends of the side aisles from the central presbytery were extended westward as substitutes for the two eastern columns upholding the dome, but the essentials of the plan were always retained. Subsidiary domes were sometimes added, either in place of the vaults on the arms of the cross, producing a true five-domed type such as St. Mark’s Cathedral at Venice, or placed above the eastern and western extremities of the side aisles, producing a type called the quincunx. These domes were usually comparatively small and were set on drums, which tended to become narrower and taller with the progress of time. The eastern extremities of the side aisles formed chapels which played an important part in the liturgy, that to the north being termed the prothesis and that to the south the diakonikon. Both the chapels and the main sanctuary were separated from the body of the church by a screen, which also became taller and heavier until it developed into the massive iconostasis that constitutes such a characteristic feature of Orthodox churches today. As in earlier periods, the lower portions of the walls were, in the richer churches, covered with marble slabs; and there were elaborately carved cornices and capitals, though ornament was always rather formal and in low relief. The main church at the monastery of St. Luke near Delphi, in Greece (c. 1050), is the most complete surviving example of the type.

The late Byzantine period (1204–1453)

Quite a number of buildings from the late Byzantine period survive in Istanbul, Thessaloníki, and throughout Greece and the Balkans. In general they are on a small scale and follow the plan of those of the middle Byzantine period. But their appearance changed quite considerably, with the domes becoming smaller and higher, while the wall surfaces of the exterior were usually elaborately decorated, either with intricate patterns in brickwork or by setting glazed pottery vessels into the wall to form friezes similar to work in tile. In Constantinople elaborate blank arcading also played an important role, as, for example, in the church of the Pammakaristos Virgin (Mosque of Fethiye; c. 1315). The building material varied with the locality, though generally brick was preferred to stone. In the details of planning and in the handling there was considerable regional variation, and numerous local styles may be distinguished. Grandeur was generally lacking—except perhaps in the churches set up for the Comnene emperors of Trebizond, a state on the south side of the Black Sea, ruled by Greeks (1204–1461)—but all the buildings have considerable charm and deserve fuller consideration than they have sometimes received. Good work was done even after the Turkish conquests, especially on Mount Athos, Greece, and in the Romanian region of Moldavia, where the large-scale painted churches, which mostly date from the 16th and 17th centuries, are often both magnificent and very beautiful.

Even at this period, little is known of secular architecture, but a portion of the Blachernae Palace at Constantinople may be noted, as well as the monasteries, particularly those on Mount Athos; though they have been much restored or even wholly rebuilt, the general layout of most follows a Byzantine scheme.