Castillo de San Pedro de la Roca.

Perched on a 60-meter-high rocky promontory guarding the entrance to Santiago Bay, this imposing 17th-century fortress is the most complete and best-preserved example of Spanish-American military architecture. Built to defend the city from naval attacks and pirates, the fort’s genius lies in its organic design: rather than flattening the terrain, its terraces, bastions, and batteries step down the cliff, mirroring the natural shape of the rock. Visitors can explore the interior museum’s displays of weapons and historical artifacts, but the real draw is walking the upper levels. From here, the defensive logic of the site becomes clear, offering sweeping, unobstructed views of the coastline and the Caribbean Sea. Located about ten kilometers outside the city center, it makes for a rewarding half-day trip.