St.Petersburg can sometimes be called "museum city", that is all cause of accumulation of lots amount of world-famous museums, such as "Russian museum" that was designed by Rosso. There is also a Hermitage that is considered to be the greatest treasure-house in the world. "The winter palace" is situated in St.Pet. , it was constructed by Rustrelli. There are also Peter's and Paul's Cathedral. The Fortress that is used to be a prison, however is a Russian famous museum. And the most famous emblem of St.Pet. are bridges.This city is known as City of Bridges.