Located on the southern side of the entrance to the Port of Maó, in Cala Sant Esteve (Es Castell), it was built by the British between 1710 and 1726. The last renovation dates from the end of that century. Along with the Castle of San Felipe and the Stuart or d'en Penjat Tower, it served to protect the entrance to the Port of Maó.
Most of the structure is excavated into the rocky subsoil, so the visit begins with the underground galleries, countermines, and rooms carved into the rock, and then continues through the moat and the upper area, from where visitors can enjoy an exceptional view of the historical area of the Port of Maó.
An exhibition places the visitor in the era of the sieges of Fort Marlborough, explaining the history of Menorca and Europe throughout the turbulent 18th century.