The strategic importance of the port of Mahon was made obvious during the 18th and 19th centuries. Once the Sant Felipe castle had been destroyed, leaving the island defenceless, the Isabel II fortress was built between 1848 and 1875 to counter the recurrent threat of different foreign powers again occupying Minorca.
The fortress was designed following the designs and ideas of military engineer Montalambert, who concentrated fire on the inward angles and then placed strongholds and casemates at different points at that location to defend the escarpments and the moat. Thus, the La Mola fortress, thanks to its polygonal front, provided defence against attacks from the sea and over land. The hornwork, being the centre of the fortress, defended the land side on its right and the sea side on its left.
In later years, La Mola underwent new extensions with the installation of new artillery posts, especially the Vickers 38 cannons that were installed during the Civil War and proved an unbreachable defence for any fleet approaching the island. This fort can be visited and different activities are organised within the grounds, such as astronomical observation, photography competitions, exhibitions, antiques fairs, etc.