On the eastern edge of the old town sits the Fort of St. John, known to locals as the Fort of St. Ivan. Once an important part of Dubrovnik's defenses, this imposing structure now houses several modern attractions to keep visitors entertained.

In the upper area is the Maritime Museum of Dubrovnik featuring displays of Dubrovnik's maritime past illustrated through model boats and naval artifacts, while the lower area contains the Aquarium of Dubrovnik with its many interesting displays of local and exotic fish, as well as a superb collection of seahorses.