Castillo San Felipe de Barajas

San Felipe de Barajas is the largest Spanish fortress in the Americas — a massive stone fortification on the Hill of San Lázaro that was built between 1536 and 1657 and successfully repelled every attack launched against it, including the 1741 siege by British Admiral Edward Vernon (who arrived with 186 ships and 23,600 men — one of the largest amphibious forces assembled before D-Day — and was defeated by a Spanish garrison of 3,000 led by the one-eyed, one-armed, one-legged commander Blas de Lezo).

The fortress's most impressive feature is its tunnel system — a network of underground passages designed so that any sound in the tunnels would echo to the defenders, making a surprise underground attack impossible. Walking through the tunnels (some lit, some dark enough to require a phone flashlight) provides a visceral encounter with colonial military engineering.

The fortress provides the best elevated view of Cartagena — looking across the old city's rooftops to the Caribbean, with the modern city visible to the south and the mangrove-fringed bay stretching inland.