Istanbul's Church of the Pantocrator, now a mosque named Zeyrek Camii, is a former monastery church and one of the most important historic landmarks of the Byzantine period.
However, the structure is in a sad state of neglect so a detour here may only be worthwhile in tandem with a stroll through the narrow streets of the Zeyrek neighborhood.
Dedicated to St. Saviour Pantocrator, the monastery was founded by Empress Eirene, wife of John II Comnenus, who completed the south church prior to her death in 1124. She was also the first to be buried here (her sarcophagus was moved in the 1960s to the Archaeological Museum, but now resides in the exonarthex of the Ayasofya).
The northern church was added by the emperor (her husband) after Eirene's death, and dedicated to Virgin Eleousa, the Merciful or Charitable.
The emperor also had the churches connected through the jerry-rigging of a chapel between the north and south church, which also required the demolition of part of the exterior walls of the two buildings.
The church was converted to a mosque in the 15th century.
What to See
The building is actually a composite of two churches and a chapel, making it the second largest church in Istanbul after Ayasofya.
Inside, the building preserves some of its original decoration (marble pavement, door frames in the narthex, marble apse). Restoration is ongoing. The 15th-century minbar (pulpit) is composed of recycled fragments of Byzantine sculpture.
To the east of the building is the Ottoman Konak, restored and opened as a fine restaurant and tea garden, the Zeyrek Hane. It's much out of character with the rest of the neighborhood, but the food is good and includes a view both of the city and of the Zeyrek Camii. The tea garden is decorated with Byzantine columns, capitals, mosque toppers and other marbles of unknown provenance.