Standing proudly in Sofia's sprawling heart, this cathedral is a marvel of Neo-Byzantine architecture. Adorned with striking gold domes and intricate mosaics, it commemorates the 200,000 Russian soldiers who died in the Russo-Turkish War of 1877–1878. This monumental edifice can house 5,000 worshippers, making it one of the largest Eastern Orthodox cathedrals in Europe. Be sure to look out for its imposing 53-metre high bell tower, which boasts a superb 12-bell carillon system. Stepping inside reveals a treasure trove of frescoes, icons, and a serene ambience that contrasts with the bustling city outside.