Petrovaradin Fortress (Serbian: Петроварадинска тврђава or Petrovaradinska tvrđava, pronounced [pɛtrɔv̞arǎdiːnskaː tv̞ř̩dʑav̞a], Hungarian: Péterváradi vár, German: Peterwardein) is a fortress in Novi Sad, Serbia. It is located in the province of Vojvodina, on the right bank of the Danube river. The cornerstone of the present-day southern part of the fortress was laid on October 18, 1692, by Charles Eugène de Croÿ. Petrovaradin Fortress has many underground tunnels as well (16 km of uncollapsed underground countermine system).