 The church featured ample exterior and interior decoration . While the facades were decorated with arches and ceramic tiles , the interior floor mosaics were made of white , yellow and pink marble as well as semi @-@ precious <unk> like <unk> and <unk> . The interior walls were covered with frescoes and mosaics . However , none of the interior decoration has survived . During the church 's 20th @-@ century reconstruction , its interior was <unk> by artist <unk> <unk> , who depicted important moments of medieval Bulgarian history in a modernist style . Due to these murals , the church has never been <unk> and remains inactive . The facade of the cathedral also includes a stone with a donor 's inscription of a Bulgarian ruler , which ended up as part of the building material . 
