Architectural reinterpretation of the byzantine buildings converted into mosque in the Historical Peninsula of Istanbul depending on the data revealed during the repair and restoration processes

It is clear that Istanbul, as the capital of Rome (Eastern Roman/Byzantine), was the center of large public building organizations. Currently Fatih or so-called Suriçi region, perhaps the most important region of Istanbul in terms of ancient monuments, has been home to Byzantine period structures. The Lala Hayrettin Ağa/Çelebi Mosque (Chalkoprateion) and the İmrahor İlyas Bey Mosque (Stoudion) in the thesis studied are actually basilicas that has been surviving since the Hellenistic period to the Late Antiquity period, which we can interpret as imperial structures. When we look at other buildings, we see buildings of church origin that evolved from the basilica to the cross plan over time. The Atik Mustafa Pasha, the Koca Mustafa Pasha Mosque, the Kalenderhane Mosque, the Gül Mosque, the Monastery Mosque and the Kefeli Mosques are examples of this evolution. The buildings designed according to the closed cross plan (cross-in plan) are the Messi Pasha Mosque, the Eski Imaret Mosque, the Fenari İsa Mosque, the Zeyrek Church Mosque, the Vefa Church Mosque, the Hirami Ahmet Pasha Mosque, the Kariye Mosque. Apart from these, ciborium plan structures such as the southern structure of the Fethiye Mosque and the Fenari İsa Mosque are examples of a separate architectural development. Kariye Mosque displays a transition between these two types. While the Little Hagia Sophia Mosque has a different combination with its octagonal plan, the Şeyh Süleyman and the Sancaktar Hayrettin Masjids are examples of tomb structures with octagonal and cross-in square plan schemes. While the Kasım Ağa Masjid is a different structure that does not belong to any group and does not have the identity of a religious building, the İsakapısı Masjid has the form of a chapel or refectory building with three apses, although it has a single nave. Until today, various publications have been made on the history of architecture about the Byzantine buildings converted into mosques in Istanbul. The aim of my thesis is to evaluate the revealed data obtained through technical studies and to contribute it to the science of art history through a new perspective and aspect that have recently emerged or have never been examined before or have not been examined adequately. All of the buildings that have been examined in the study belong to the Byzantine past of Istanbul. On-site excavations and some documents of some buildings other than the ones mentioned above, have enabled us to reach different conclusions. It has been explained within the scope of the thesis with the help of archaeological evidence that three buildings, which have been generally assumed to belong to the Byzantine period in the literature, are entirely from the Ottoman period. While the periodic and architectural developments of the buildings other than those are explained, especially the XXth century repairs are discussed in the light of Foundation documents. The main interventions made during the period when modern interventions began and some Ottoman additions that were removed from the buildings were pointed out. The physical properties that changed are discussed in detail throughout the conclusion section. Additionaly, the restoration practices were discussed depending on the projects prepared in of the first quarter of the 21st century and some conclusions were reached regarding the architectural design processes, additional spaces and historical background of the buildings depending on the new findings. These results are of authenticity since they are based on recent data. In the conclusion and evaluation section, which we prepared depending on the content of the thesis in general terms, the changes in the functions of the buildings, the mosque-lodge dilemma; the findings of archaeological researches; the contributions of old restorations, changed forms with projects and new findings obtained through recent restorations/projects to the buildings mentioned above are discussed. Being involved in the latest restoration works and projects of most of the buildings in the subject, with the help of on-site observations and comparisons and witnessing data not available in the literature, has provided significant benefits in the internal evaluation of most of the buildings. Solutions to some problems and suggestions on the basis of buildings were made based on this data. For this reason, the conclusions reached can be considered as a stepping stone for other scientific studies, an important step towards solving different problems or making different contributions.