The results of the investigation prior to the excavation work in the Castle of San Luis, in Estepona (Málaga, Spain) are presented. It is a coastal fortress built in the last quarter of the sixteenth century, in the context of the reorganisation of the defense of the western coast of Malaga after the Moorish rebellion of 1568. After analysing the available literature, we propose that it was designed by the Engineer Juan Ambrosio Malgrá, Maestro Mayor de obras del Reino de Granada.

The Castle of San Luis is devised as an add-on construction on the southern front of the walls of Islamic origin, dominating the natural anchorage of the Rada beach. Its most prominent elements are three bastions, two of them with casemates, and a large main square. However, various defects in the design and execution of the works, added to the insufficient provision of artillery and garrison, affected the effectiveness of the fortification throughout its history.

In the middle of the eighteenth century, part of the Castle of San Luis is restructured as a cannons’ battery. Following the damage caused by the Lisbon Earthquake, in 1755, and by the French and English blastings in 1812, during the second half of the nineteenth century much of the castle disappears, leaving only the cannons’ battery, which is incorporated as a courtyard in height as an add-on to a house built at the end of the nineteenth century.

At present, after several decades of abandonment, excavation works have been undertaken on the remains of the battery, after which the site will be prepared to be used as a museum.