Once protecting the eastern edge of the city, nowadays the fort houses several attractions - the Maritime Museum and the Aquarium.
Wikipedia (Croatian) https://hr.wikipedia.org/wiki/Tvr%25C4%2591ava_Sv._Ivan_u_Dubrovniku
Address Tvrđava svetog Ivana, 20000 Dubrovnik, Croatia
Coordinates 42°38'23.748" N 18°6'44.924" E