Castillo de la Real Fuerza is the oldest bastioned fortress in the Americas, completed in 1577 to defend Havana's harbour. Its low stone walls stand just off the Plaza de Armas, with good views across the water and back into Old Havana.
The fort now houses Cuba's main maritime museum. Exhibits cover pre-Columbian navigation, Havana's royal shipyard, colonial sea trade, and the huge warships built here for the Spanish crown. It is both a major historic site and a useful break from the heat of the old town streets.