One of the largest and best examples of Byzantine architecture still standing today, the Zeyrek Mosque began service in the twelfth century as an Eastern Orthodox monastery. It grew dramatically over the following decades, acquiring a library, a hospital, a second church, a courtyard, and a tomb in less than 100 years. During the Latin occupation of the city, the complex was the Vatican Clergy's see, until the restoration of the Palaiologos dynasty reinstated its Orthodox monks.
Once the Ottomans took over, the entire building complex took on a multi-faceted, multicultural role. Muslims used one of the buildings as a madrasah, while Christians were still permitted to worship in the church's facilities.