During the summer months when the river isn't frozen, the bridges across the Neva open at night to allow ships to pass up and down the river. Bridges open from May to late October according to a special schedule. Make sure you check the schedules and don't get caught on the wrong side of the river after 2 a.m., or you will be stranded on the wrong side of the river until the drawbridges are lowered between approximately 4:30 a.m. and 5 a.m.
Draw bridges(night city tour)
St. Petersburg was built on the delta of the River Neva and is spread out over numerous islands of varying sizes, frequently prompting the nickname the "City of 101 Islands". Over the centuries numerous bridges were built to connect these islands across the various tributaries of the Neva and the city's many canals (Moika, Fontanka, Kanal Griboedova, etc.).