Petrovaradin Citadel information
Towering over the river on a 40m-high volcanic slab, this mighty citadel (tvrđava ) is aptly nicknamed 'Gibraltar on the Danube'. Constructed with slave labour between 1692 and 1780, its dungeons have held notable prisoners including Karađorđe (leader of the first uprising against the Turks and founder of a dynasty) and Tito. Have a good gawk at the iconic clock tower: the size of the minute and hour hands are reversed so far-flung fishermen can tell the time.
Within the citadel walls, a museum offers insight (sans English explanations) into the site's history. The museum can also arrange tours of Petrovaradin's creepy – but cool – underground passageways.