Defensive fortification located on an islet. The watchtower from 1610 is the oldest structure. The walls and internal dependencies date from the 18th century. The layout is mostly straight, except for the semicircular battery that surrounds the tower to the east. The military dependencies are concentrated in the northern part. It was part of a broader defensive system, supported by three batteries on land at Punta del Boquerón (Urrutia, San Genís, and Aspiroz), illustrating the logic of integrated defense of the Bay of Cádiz, combining island and coastal positions for effective control of the caño. The site is described as of great beauty and cultural, historical, natural, and landscape value.