The building of this complex consisting of a church, a monastery and a hospital was initiated by Byzantine Empress and Hungarian princess Saint Piroska / Eirene Komnenos (1084-1134), and was built from 1118-1136. It is the second biggest Byzantine structure still standing in today’s Istanbul after Hagia Sophia. After 1453, it was called Zeyrek Molla Mosque. Although the building is serving as a mosque today, the features of the original Christian church are well visible. The last decades has seen many restorations here including the Byzantine elements as well. The building includes a famous mosaic floor, the so-called opus sectile. Empress Eirene was buried here – her alleged sarcophagus was later brought to Hagia Sophia.