St. Petersburg The most important and interesting sights of St. Petersburg: Peter and Paul Fortress is located on the Hare island and is the historical core of the city. Kazan Cathedral is one of the largest religious buildings in St. Petersburg. The Palace Square (in 1918-1944 - Uritsky Square) is the main square of St. Petersburg and a single architectural complex. The ensemble of palaces and parks of Peterhof - "the capital of fountains" (total in the parks of Peterhof 4 cascade and 176 fountains). St. Isaac's Cathedral is a unique monument of Russian architecture and one of the best cathedral churches in Europe. The Hermitage Museum and much more.