Shlisselburg, formerly Oreshek and Petrokrepost, is a town in Kirovsky District, Leningrad Oblast, Russia, located at the head of the Neva Ri…Shlisselburg, formerly Oreshek and Petrokrepost, is a town in Kirovsky District, Leningrad Oblast, Russia, located at the head of the Neva River on Lake Ladoga, 35 kilometers east of St. Petersburg. Population: 13,170 ; 12,401 ; 12,589.