El Morro Castle, completed in 1589 at the entrance of Havana Bay, is the fortress that defined Havana's defensive geography for three centuries — a dramatic promontory fortification with a lighthouse, thick walls, and views across the bay entrance that make clear why Spanish engineers chose this site. Together with the Fortaleza de San Carlos de la Cabaña on the same headland, it forms the largest colonial military complex in the Americas.
Access is by ferry across the harbour from the terminal near Plaza de San Francisco (a few minutes) or by taxi through the harbour tunnel. The walk along the headland between El Morro and La Cabaña takes about thirty minutes and offers the best views of the Havana skyline — the Capitol dome, the waterfront hotels, and the full curve of the Malecón — available from anywhere. The castle itself has a small museum covering Cuban military history. The lighthouse can be climbed for a fee.