 The Patriarchal Cathedral features a triple apse , the central part of which matches the apse of the original basilica on the site . The three @-@ <unk> church follows the traditional Byzantine cross @-@ in @-@ square design . Built out of crushed stones and mortar with limited brickwork , it measures 26 by 12 metres ( 85 ft × 39 ft ) . The cathedral includes two <unk> , a bell tower and two other premises attached to the south church wall . The presence of a bell tower is considered to be a rarity in Balkan church architecture . Six columns support the interior and distinguish the altar from the cella ( <unk> ) . It is unclear whether the church housed a <unk> ( stone <unk> for the clergy ) in the apse , as there are doubts that its remains may actually be part of the older basilica . 
