Situated on the little island, the defensive Sancti Petri fortification was once one of a series of forts that protected the inlet, Caño de Sancti Petri. Of irregular shape and in the Moorish style, it dates from the 13th century. During the 1st century, the Phoenicians settled on the island, founding a temple dedicated to Melqart, their god. When the Romans arrived they dedicated the temple to Hercules.
The castle's watchtower is the oldest building, while the walls and the interior date from the 18th century. The castle was in an advanced state of deterioration, but the authorities of the municipalities of San Fernando and Chiclana de la Frontera funded a major rehabilitation programme.
References:The Broch of Clickimin is a large and well preserved, though somewhat restored broch near Lerwick. Originally built on an island in Clickimin Loch (now increased in size by silting and drainage), it was approached by a stone causeway. The water-level in the loch was reduced in 1874, leaving the broch high and dry. The broch is situated within a walled enclosure and, unusually for brochs, features a large 'blockhouse' between the opening in the enclosure and the broch itself. Another unusual feature is a stone slab featuring sculptured footprints, located in the causeway which approached the site. Situated across the loch is the Clickimin Leisure Centre.