Empress Irene, the wife of John II Comnenus , founded the Church of the Pantocrator ("Christ the Almighty") during the 12th century. This hulk of Byzantine masonry was once the centrepiece of one of the city's most important religious foundations, the Monastery of the Pantocrator. As well as a monastery and church, the complex included a hospice for the elderly, an asylum and a hospital. In this respect it prefigured the social welfare system provided by the great imperial mosque complexes that the Ottomans later built in the city .

The church, now a mosque, boasts a magnificent figurative marble door. It is composed of three interlinked chapels. The one with the highest dome was built by Empress Irene. Emperor John II added another as a mortuary chapel when Irene died in 1124, and he later filled the area between with a third apsed chapel. The rest of the Comnenus dynasty and many of the Palaeologus imperial family were interred within these chapels.

Shortly after the Muslim conquest in 1453 , the building was converted into a mosque. A caretaker may let you in outside prayer times in the afternoons.