Boyana Church in Sofia, Bulgaria’s Boyana quarter, is a Bulgarian Orthodox church, famous for the frescoes housed within its inconspicuous medieval walls. Photo Source: Todor Bozhinov / Тодор Божинов (own work / собствена творба) [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0], via Wikimedia Commons