Built by African slaves on the Hill of San Lázaro, just outside Cartagena, this small fort was meant to deter potential invaders. Its tunnels, bulkheads, turrets and sloping walls rendered it practically impregnable and make it one of the most formidable strongholds ever built by the Spanish colonists. A statue of Don Blas de Lezo, commander-in-chief of the fort at the time of the Battle of Cartagena (1741), is installed opposite the fortress.