Château de Blanchefort, Castle ruin in Rennes-les-Bains, France

Château de Blanchefort is a ruined fortress on a white rock peak above Rennes-les-Bains, overlooking the confluence of the Sals and the Rialsesse. Only traces remain: curtain walls around the courtyard, the footings of a trapezoidal building, the well-preserved foundations of a cistern at least two metres deep, and those of a square keep seven metres a side with walls 1.5 metres thick.

First mentioned in 1067 as the castrum de Blancafortis, the castle belonged to the abbey of Jaffus in 1100 and to the abbey of Alet in 1119. In 1209 Simon de Montfort took it from the Cathar-aligned lord Guillaume de Blanchefort, and Pierre de Voisins imposed heavy taxes. Enlarged in the 14th century, it lost its frontier role after the 1659 Treaty of the Pyrenees and was abandoned by 1713.

The name Blanchefort comes from the white rock of the peak, "le fort blanc". A legend of 1130 holds that the Templars ran a gold mine here, but that the gold actually came from a Visigothic treasure found in the castrum. Another legend credits Blanche de Castille, who came to Rennes-les-Bains, with ordering the castle's construction.

The climb to the castle is challenging and requires good footing and protective clothing against thorns and thick vegetation. Visitors should arrive early in the day and bring plenty of water, as there are no facilities on site.

The entrance to the castle courtyard was accessible only by ladder, as the main door sat several meters up on a cliff face. This unusual access control made the fortress feel nearly impregnable to attackers.