The Swedish army built a modern fortress during the 1640s with five bastions and two gates.  There were 120 cannons and mortar throwers, barracks for soldiers, flats for officers, a garrison church and warehouses for food at munitions.  After the Great Northern War in 1710, the fortress was taken over by the Russian army.  After the Soviet occupation in 1940, the Soviet navy took over the fortress.  Alongside it is a former Soviet army facility with abandoned buildings and a monument to sailors who served in submarines.  The fortress is open for tours on Saturdays and Sundays.