The Fort de la Guàrdia is a citadel of the xvii century that dominates the town of Prats de Molló, in Catalonia from north

It is located only 325 meters from the town, about 100 meters higher, towards the northeast. It is only thirteen kilometers from the state border. Apart from guarding the town, its purpose was to guard the Ares Pass.

Capital of Alt Vallespir, Prats de Molló became an important strategic place after 1659, the date of the Treaty of the Pyrenees, which gave the old County of Roussillon to the French State. The town was fortified by the marshal of Louis XIV of France, Sébastien Le Prestre, who also built the Fort of the Guard, overlooking the site. Vauban built the fort in the place where there had been the medieval watchtower, from the xiii century, of the Guard, which is included in the new construction; the old tower occupies the central place of the modern fortification.

The Guard Tower has been documented since 1307, and it was around it that the modern Fort was built. It has a circular plan, and its height reaches 9 meters. The internal diameter is 3.2 m at the level of the first floor, with a wall thickness of 145 cm. It has two interior rooms, covered with a dome. Although it now has an entrance door at ground level, the original is at floor level, faces south and is formed by a slightly lowered arch, formed by slabs in the shape of a book fold. On this first floor there is another door, towards the north, which communicates with the annex building. An open staircase inside the perimeter wall allows access to the upper floor.

The Guard Fort was classified as a French historical monument in 1925.