Vlacherna was the catholicon of a male monastery. It was built in 1224-1230 to replace an older church (from the early 10th century), whose remains were incorporated in the new building. If you observe the south wall and the south apsis (the left of the three on the church’s east side) you will notice the different building style of the older church (the stones are irregular and kept together with ample mortar). Vlacherna is a three-aisled basilica with one dome above each aisle (only the main one belongs to the original plan, the others were added at a later date). Soon after its completion, the monastery became all female, but remained an informal haven for deposed emperors in trouble.