Lotrščak Tower
Formerly the entrance to the fortified medieval town of Gradec, Kula Lotrščak now houses a multilevel gallery with occasional exhibits of contemporary art. Each day at noon, a small cannon is fired from the top of the tower in memory of the times when it was used to warn of the possibility of an Ottoman attack. You can climb the tower partway via a spiral wooden staircase for a look into the gallery rooms (which occupy several floors), or you can ascend all the way to the observation deck for splendid views of Zagreb and its environs. You can also take the 216-foot Zagreb Funicular (the world's shortest) straight to the tower.
