The Dubrovnik Aquarium occupies the ground floor of the St. John Fortress at the entrance to the old harbour, a 16th-century structure that now serves a rather different purpose. The collection focuses on the marine life of the Adriatic, with tanks holding local fish, sea turtles, moray eels, and the occasional shark alongside explanations of the ecology of the Dalmatian coast.
It is a modest facility by international standards, but the setting inside the old fortress walls is appealing, and for children it is an effective hour out of the sun. The building also houses the Maritime Museum on the upper floors, which covers the seafaring history of Ragusa and Dubrovnik with ship models, navigational instruments, and documents about the republic's once-extensive merchant fleet.