Octagon plan type in Byzantine architecture: İstanbul Saints Sergius and Bacchus Church (little Hagia Sophia Mosque) example

In this study, the octagon plan type in the Byzantine architecture and the earliest church example in Istanbul today, the Church of Sts. Sergius and Bacchus (Little Hagia Sophia Mosque) is discussed. Istanbul hosted many civilizations and important empires such as Rome, Byzantine and Ottoman. In this regard, the city has been handled in three sections as Byzantion, Constantinople and the history of Istanbul. The number eight, which forms the geometric form of the octagon plan type in Byzantine architecture, and its importance for Christianity, and the purpose of the octagon-planned structures encountered in Byzantine religious architecture were mentioned. The church is one of the most important example of Byzantine architecture that has survived to the present day. However, the date of construction, for what purpose it was built the building or building complexes around it, and the location of the church according to them are unclear issues. Many important researchers have expressed their opinions on these issues. As a result of the excavation and restoration work carried out between 2003-2006, some parts of the building that were left in the dark were illuminated. In the evaluation part, the samples of octagon plan type that examined, the inscription, the monograms, the architectural plastic elements found in the excavations and the opinions of the researchers were discussed.