Shlisselburg (Шлиссельбург), formerly Oreshek or Orekhovy (Swedish: Nöteborg, Finnish: Pähkinälinna) is an island, town and fortress in Central Leningrad Oblast. The fortress and the town centre are UNESCO World Heritage Sites.
Shlisselburg is a town on the southwestern shore of Lake Ladoga, Europe's largest lake, at the head of the Neva river. It is famous for its fortress, first named Oreshek and finished in 1323, and for the Treaty of Nöteborg, a piece treaty between Russia and Sweden that was signed here in the same year.
The original wooden fortress was built on behalf of the Novgorod Republic in 1323. Sweden took the fortress in 1348 and Novgorod reconquered it 1451. It was largely destroyed, and the Muscovy, who had absorbed Novgorod in 1478, built a stone fortress instead. Sweden took it in 1611. When Peter the Great conquered it 1702 he renamed it Schlüsselburg, meaning it was the key to Neva. Transliterated via the Cyrillic script the name became Shlisselburg.