The fort was named after Saint James the Great (Santiago in Spanish), the patron saint of Spain, whose relief adorns the façade of the front gate.[1][2] It is located at the mouth of the Pasig River and served as the premier defense fortress of the Spanish Government during their rule of the country. It became a main fort for the spice trade to the Americas and Europe for 333 years. The Manila Galleon trade to Acapulco, Mexico began from the Fuerte de Santiago.[citation needed]
The fort has a perimeter of 2,030 feet (620 m), and it is of a nearly triangular form. The south front, which looks toward the city, is a curtain with a terreplein, flanked by two demi-bastions - the Bastion of San Fernando, on the riverside, and the Bastion of San Miguel, by the bayside. A moat connected with the river separates the fort from the city. Near the beginning of the north face, instead of a bastion, a cavalier called Santa Barbara was built with three faces of batteries, one looking seaward over the anchorage place, one facing the entrance, and the third looking upon the river. The latter is united with a tower of the same height as the walls, through which there is a descent to the water battery placed upon a semicircular platform, thus completing the triangular form of the fort.[3]