City/Region: San Juan. The mighty six-level fortress of San Felipe del Morro, built in 1540, towers 140 feet (43m) above the sea on San Juan Bay, its 18-foot thick (5m) walls having proved a worthy defense against invasion. The largest fortification in the Caribbean, it is a maze of tunnels, dungeons, barracks, lookouts and ramps, offering spectacular views from top its ramparts. Also in Norzagaray Street, Old San Juan, is El Morro's partner in defending the city, Castillo San Cristobal, built in the 17th century to a confusing and intricate modular design.

Hours: Forts open daily 9am to 5pm (June to November), 9am to 6pm (December to May). tours are available in English and Spanish.

Admission: Free

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