San Gabriel Castle is located on a small island that can be reached on foot via the Las Polas Bridge; It is a small drawbridge with two cannon launchers over its columns. It was initially built as a wooden fortress which proved insufficient for any defensive purposes. It was eventually torched by barbarian pirates and then replaced by a stone fortress in the sixteenth century. It played a vital role in protecting the port and the city. The castle is designated as a National Historic Monument and houses a small ethnographic museum.