Petrovaradin Fortress

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. The cornerstone of the present-day southern part of the fortress was laid on 18 October 1692 by Charles Eugène de Croÿ. Petrovaradin Fortress has many tunnels as well as over 16 kilometres of preserved underground corridors and countermine system.

In 1991 Petrovaradin Fortress was added to Spatial Cultural-Historical Units of Great Importance list of the Republic of Serbia.

Source: Wikipedia