1. Aya Sofya Camii identified with the byzantine church of Haghia Sophia

The basilica in the center of Nicaea (modern Iznik), at the intersection of two ancient main streets, is now called Aya Sofya Camii, and its identification with the byzantine church of Hagia Sophia is widely accepted.¹

According to the historical sources, the church of Haghia Sophia in Nicaea was in 787 the site of the Seventh Ecumenical Council, which was convened to adjudicate on the issue of Iconoclasm and give an end (which would prove only temporary) to a dispute over which the Byzantine society divided for half a century. The church of Haghia Sophia was chosen because, according to the sources, it was the city’s cathedral and its largest church. The location of the basilica preserved until today in the exact center of the city, along with the fact that it is the largest one among the known churches of Nicaea (which seems to have been the case already from the 14th century), support the identification of Aya Sofya Camii with the metropolitan church.

On the other hand, some scholars, like C. Foss, argue that this identification remains problematic, for the structure is apparently inadequate to have housed such a large council: more than 300 bishops and a great crowd of monks were supposed to have assembled in front of the ambo and attended the seven sessions of the Council. The evidence of the turkish name also seems rather uncertain, since the structure has been named so only in the 20^th century, while up to the 19^th century it had been known as the Mosque of Orhan, and in even earlier times it apparently bore the name Ulu Camii (Great Mosque). It is therefore possible that, with all those changes of names, the memory of the church's original dedication did not survive. Furthermore, according to C. Foss, the fact that Hagia Sophia is not mentioned after 1065 maybe suggests that the church was desroyed by the earthquake of that year and was never rebuilt. Such a view would provide an explanation on why had the patriarch his seat elsewhere during the Laskarid period.²

2. The church's building's phases

The various building phases of the structure, which dominates the centre of the city of Nicaea, are marked in the successive repairs discernible in the surrounding wall. The church is an oblong three-aisled basilica, today measuring 30x22 m approximately; however, in calculating the dimensions of the Early Christian basilica we should take the narthex into consideration, with the addition of which the church must have measured approximately 37m. It comprises a nave with a large apse and side aisles which, after the Middle Byzantine rebuildings, end in small domed chambers without eastern apses. The narthex that it originally had in its western side, some 6.50m in width, was immediately accessible from the street, as there was no atrium on its western end, the church being located on the crossroads (fig. 2).

The appearance of the building today is the result of multiple periods of repairs and rebuildings, for which various interpretations have been proposed.³ All agree that the lower levels of the original building, most close to its foundations, were constructed with regular courses of marble ashlar (these can still be discerned clearly in certain parts of the building), with a superstructure in brick. This original period dates to the 5^th or 6^th century. This is probably the church that is mentioned in relation with the 740 earthquake, which is said to have left only one church standing. We do not know the name of that church, but, as far as we know, no other Early Christian church has survived in Nicaea in the Middle and Late Byzantine periods.

The Early Christian church was divided into three aisles by two colonnades with marble columns, probably taken from the abundant material that the earlier Roman buildings of the city offered. In its eastern side, the wide nave ended in a semicircular apse with a rather tall synthronon (fig. 3), unlike the two flanking aisles which ended up in walls and not in smaller apses (fig. 2, ground plan on the left). The openings of the lower windows on the two side walls, north and south, date to the church's first phase and are still discernible, although by the Middle Byzantine period they were already filled in and partially buried. Finally, a chapel known only through excavations on the south side of the church, adjoining its south wall, should also be dated to the church’s first building phase. Peschlow argues that the Early Christian basilica was erected on the site of an ancient temple. This is indicated by the fact that the basilica’s walls incorporate a large amount of earlier building material, large, finely cut blocks, as well as by the building’s prominent position within the urban tissue, a site that was certainly taken up previously by an earlier important structure.⁴

Later on, and at various times during the Middle Byzantine period, the church was extensively rebuilt and repaired. The basic plan of the three-aisled basilica was preserved; its flanking aisles were, however, divided by sturdy long pillars made of brick, which replaced the earlier light colonnade (fig. 2, ground plan on the right). This modification was needed for the support of the new vaulting system of the church, the central dome, the side arches and the smaller cupolas of the corner chambers, in accordance with the dominant architectural trends of that period (fig. 1). The new floor was constructed approximately a meter above the earlier one, the apse was redesigned to become polygonal on the exterior, and the synthronon was partially buried, along with the side walls. The chambers at the east end of the side aisles were covered with domes, thus forming two semi-independent chapels, as we shall see later. All along the walls extensive repairs were made, for which bricks were used and building techniques strongly reminiscent of the Constantinopolitan masonry were employed (fig. 4, fig. 5). Even the external cross-shaped chapel received a new marble floor, of marble in secondary use, finely decorated with opus sectile.

This extensive rebuilding of the church should be in their largest part dated to the 11^th century, when the church acquired its standard Medieval form. This hypothesis was also confirmed by A.M. Schneider, who studied the building and managed make some small trial excavation. He concluded that the pillars and the domed chambers were contemporary, representing a single building phase (of the 11^th century) and that only partial and minor repairs can be dated later.⁵

On the contrary, C. Foss suggests a dating of the church’s phases based on the comparison of the masonry types observed in the building with the different masonry types found in the city walls. According to C. Foss, this comparison proves right N. Brunov’s earlier theories, who had distinguished several different phases of rebuilding.⁶ According to C. Foss, every period of rebuilding is marked by its mortar. Thus the brickwork of the central piers and the dividing walls of the church bear great similarity to the towers built by Michael III, in 858: bricks are used in both masonry types, arranged in thick and slightly irregular rows, with mortar of the same colour and containing broken tiles and black pebbles in the same proportions. Therefore, C. Foss dates the main Middle Byzantine rebuilding period of the church to the mid-9^th century. The domed chambers and the rebuilding that gave the apse its final appearance must be dated to the 13^th century, according again to their masonry, which is close to that of a certain part of the city walls built by Vatatzes.⁷

3. Chapels on the east side

Among the most interesting architectural elements of the church are the two chapels, situated on the east part of the church, flanking the bema. This is an addition made either in the 11^th or in the 13^th century, when the extremities of the two side aisles were walled up and domed with their own cupolas, which still survive today (fig. 6). In any case, this particular arrangement of the chapels is not unknown in the Middle Byzantine years and, should we accept a date in the 11th century for the addition, than the monument could be placed among a group of Middle Byzantine churches including, as typical examples, Hagios Achilleios at Little Prespa and the Metropolitan church of Serres. This type of arrangement, with the chapels inscribed in the churches main ground plan, has been named ‘compact’.⁸ Little is known about the chapels' use, yet the presence of a sarcophagus in one of them may suggest that they were burial chapels, at least during their last period of use (fig. 7). The very few frescoes still surviving in this part of the church might prove helpful towards interpreting the use of the chapels.⁹

4. Opus sectile pavement

The church of Haghia Sophia must have been richly decorated, but very few parts of this decoration survive today. The walls were covered with mosaics and frescoes which are now largely ruined. The most impressive decorative element of the Byzantine church still preserved is the floor’s opus sectile. A.M. Schneider was the first to detect, in 1936, a section of the opus sectile pavement in the area of the apse and the bema. It was raised on a level 1.40 m above the original floor of the Early Christian basilica, so A.M. Schneider dated it to the 1065 rebuilding period. It is a simple geometric pattern featuring repeating squares arranged around rhomboid panels¹⁰ (fig. 3).

In 1955, during the wider excavations of the monuments of Nicaea by the Turkish Archaeological Service, a second, larger section of the pavememt came to light, in the western area of the nave nearest the narthex. This is a square pavement measuring 3.60 x 3.60m, and it survives almost intact. It is made in the opus sectile technique and, according to the Turkish scholar S. Eyice, it is also to be dated to the 1065 rebuilding period.¹¹ This floor is a fine specimen of Middle Byzantine floor mosaic art. A wide border of squares and rectangles frames the main motif. The large, central square pannel is divided into two concentric circles formed by interlaced bands of white marble. The central circle frames a circular slab of green marble. Between the two large circles appear eight smaller, interlaced ones. In the spaces between the interlacing there is variform mosaic ornamentation composed of very small marble chips. The presence of the fleur-de-lis pattern which surround the central circle is interesting. Recent studies suggest that the fleur-de-lis pattern may have been the heraldic symbol of the Laskarid dynasty in the 13^th century, as it is found on coins coming from the local mints of the Empire in exile.¹² The correlation of the pavement with the Laskarid dynasty would lead to a new date of this opus sectile in the 13^th century, in the same period of repair during which, according to C. Foss, the eastern domed chambers were also built.

Nowadays, visitors cannot see these pavements, as they have been covered for their protection.

5. The fate of the monument after the Ottoman conquest