 The current building of the Patriarchal Cathedral is considered by scholars to have been built in two stages . The first stage of construction was carried out in the late 11th century or the 12th century . The cathedral was initially built as a monastery church in the middle of a monastery compound , though in the early 12th century it was already the seat of the Bulgarian patriarch . The compound suffered large @-@ scale damage caused by a fire , which necessitated the church 's reconstruction in middle of the 14th century , perhaps during the rule of Tsar Ivan Alexander of Bulgaria ( r . 1331 – 71 ) . Besides repair and reinforcement efforts , work on the church in the 14th century also included the construction of the <unk> and the bell tower . 
