|It was declared National Monument. Was built by Bautista Antonelli. Was built on one of the points jutting into San Lázaro (St. Lazarus) Cove, on the western shore of the entrance to the port. Its construction began in 1589, at the same time as El Morro Castle did. Both of them had strategic positions –they were placed in both sides of the entrance of the bay—for they would be the most important defensive systems of the city. Its ground floor is similar to any renaissance fortress, with sentry boxes on top of the ramparts as its relevant features. It was reconstructed in the 18th century to repair damages caused by the British during their siege of the city. Early this century during fine first governments of the Republic, it lodged offices of the Navy.