As in many of the surviving Byzantine churches of Istanbul, the four columns which supported the crossing were replaced by piers, and the colonnades at either ends of the crossarms were filled in. The piers divide the nave into three aisles. The side aisles lead into small clover-leaf shaped chapels to the east, connected to the sanctuary and ended to the east, like the sanctuary, with an apse. These chapels are the prothesis and diaconicon. The Ottomans resurfaced the apses and built a minaret, which does not exist any more.