Fodor's Expert Review Castillo San Felipe del Morro
At the northwestern tip of the Old City, El Morro ("the promontory") was built by the Spaniards between 1539 and 1786. Rising 140 feet above the sea, the massive six-level fortress was built to protect the port and has a commanding view of the harbor. It is a labyrinth of cannon batteries, ramps, barracks, turrets, towers, and tunnels, which you're free to wander. The cannon emplacement walls and the dank secret passageways are a wonder of engineering. A small but enlightening museum displays ancient Spanish guns and other armaments, military uniforms, and blueprints for Spanish forts in the Americas, although Castillo San Cristóbal has more extensive and impressive exhibits. There's also a gift shop. The fort is a National Historic Site administered by the U.S. Park Service and is a World Heritage Site as well. Various tours and a video are available in English.