Castillo San Cristobal (1783) defends the only land access to old San Juan. Land access to old San Juan. Castillo San Felipe Del Morro (background) and old town (left). 18th century tunnel. Chapel, mid-19th century. Cistern built beneath the fort were used to store rain water. Dormitory. Countermining tunnel, equiped with mines that could be remotely detonated to collapse the tunnel on ennemies. Galleons. Old CityCastillo San Felipe Del Morro Labels