What first impressed me at the Great Mosque of Diyarbakır was that it did not seem to belong to a single period. The weight of the black basalt, the different façades surrounding the courtyard, architectural fragments from the Roman and Byzantine periods and inscriptions added under Islamic dynasties all stand side by side. As on the city walls of Diyarbakır, the layered history of the city can be read directly in the stone.

After Diyarbakır was taken by Muslim Arab forces in 639, a major Christian place of worship in the city centre is generally understood to have been converted into a mosque. It would be misleading, however, to identify today’s Great Mosque simply with that first structure. The complex was repeatedly altered, repaired and rebuilt. A major turning point in the formation of its present architectural character came during the reign of the Great Seljuk Sultan Malik-Shah; an inscription dated 1091 is one of the most important records of this intervention.

A major earthquake in 1115, followed by fire, caused serious damage. Later repairs did more than restore the building: they added new architectural layers. Inscriptions left by successive dynasties, especially the Artuqids, now form a chronology written in stone. The mosque should therefore be understood not as the work of a single architect or ruler, but as an architectural whole formed over many centuries.

At the centre is a broad rectangular courtyard. The surrounding façades are not identical, and this is one of the complex’s most compelling qualities. On the eastern and western sides in particular, columns, arches, reliefs, inscriptions and stonework from different periods create extraordinarily rich surfaces. Spolia from Roman and Byzantine buildings appear beside Islamic inscriptions and ornament, showing how Diyarbakır’s past accumulated in layers rather than in isolated historical compartments.

The principal prayer hall extends along the southern side of the courtyard. Its width is greater than its depth, recalling the planning of early congregational mosques. The relationship with the Umayyad Mosque of Damascus has long attracted attention. Yet the Great Mosque developed a distinctly regional identity through Diyarbakır’s dark basalt, reused ancient elements and the decoration contributed by successive periods.

The complex was more than a place of prayer. The Mesudiye Madrasa beside the courtyard is an important example of early Anatolian madrasa architecture, while the nearby Zinciriye Madrasa formed part of the same religious and educational environment. For centuries the Great Mosque therefore functioned as a centre of learning as well as worship.

The sundial in the courtyard is another reminder of this intellectual history. It is traditionally associated with the great engineer al-Jazari, who worked at the Artuqid court in Diyarbakır in the late twelfth and early thirteenth centuries. Rather than claiming that the surviving sundial was certainly made by him, the connection is better treated with caution. Al-Jazari described remarkable water clocks, automata and mechanical systems in his celebrated work on ingenious devices, and his presence alone reveals the importance of medieval Diyarbakır as a centre of science and technology.

While photographing the Great Mosque, the eye inevitably moves from one detail to another. A capital may evoke the Roman or Byzantine world; an Arabic inscription beside it leads toward the Seljuk or Artuqid period; vine leaves and vegetal motifs emerge from the basalt. Yet when the courtyard is seen as a whole, none of these elements appears disconnected from the others.

For me, this is the essential value of the Great Mosque of Diyarbakır. It is not only one of Anatolia’s oldest major mosques. It is a living part of the city’s memory, carrying traces of Roman, Byzantine, early Islamic, Seljuk, Artuqid and Ottoman history on the same stone walls. What makes it extraordinary is not simply its age, but the way successive periods added their own marks without completely erasing what came before.