16. Alexander Nevsky Cathedral ( Bulgaria )

Alexander Nevsky Cathedral is a Bulgarian Orthodox cathedral situated in the Bulgaria's capital, in Sofia. Built in Neo-Byzantine style, it serves as the cathedral church of the Patriarch of Bulgaria and is one of the largest Eastern Orthodox cathedrals in the world, as well as one of Sofia's symbols and primary tourist attractions. 

The St. Alexander Nevsky Cathedral in Sofia occupies an area of 3,170 square metres (34,100 sq ft) and can hold 5,000 people inside. It is the second biggest cathedral located on the Balkan Peninsula, after the Temple of Saint Sava in Serbia.