Together with Palace Square and St.-Isaac's Square the Decembrist's Square is a part of the splendid ensemble formed by the city's central squares. It is definitely worth walking four blocks from the Hermitage to see this magnificent open space, with the dome of St.-Isaac overseeing the square, embraced by the Admiralty to your left and the classical building of Senate and Synod to your right. The latter building was designed by Karl Rossi: the most holy Synod was the supreme authority in the Orthodox church.
The square is named after the first attempt at a revolution in Russia - the Decembrists's uprising (which took place on the 14 December 1825). This rather feeble attempt was an armed uprising of Russian noblemen, "angry young people", who had defeated Napoleon a decade ago; they protested against the monarchy and serfdom and sought to establish a republican order. Most of the decembrists ended up in Siberia; five leaders were sentenced to death by hanging.
The Manege Central Exhibition Hall across the street used to be the Horse Guards' Riding School.