Petrovaradin Fortress

Petrovaradin Fortress is a historic trademark of Novi Sad, Serbia. Petrovaradin Fortress, nicknamed "Gibraltar on/of the Danube" is a fortress in the town of Petrovaradin, itself part of the City of Novi Sad, Serbia. It is located on the right bank of the Danube river.Petrovaradin Fortress has many underground tunnels as well as 16 km of uncollapsed underground countermine system.