A UNESCO World Heritage site.It is one of the most historically important Russian Orthodox Churches. For a short period in the 14th century, the cathedral was the seat of the Metropolitan, the leader of the Russian Ortodox Chuch. Originally, the cathedral was built in 1158 and had only one dome. However, the major reconstruction followed already in 1185: four smaller domes were added, and the building was considerably enlarged in order to resemble St. Sophia's Cathedral in Kiev.