Further up the Vicdessos valley from the ice age paintings of Niaux ( https://mountainsrivers.com/2014/02/23/the-ice-age-paintings-of-the-grotte-de-niaux/) is one of the less well known Cathar castles, known as Montréal de Sos. It sits on a rocky outcrop, the Vic de Sos, from which the valley gets its name. Occupied since the Bronze age, this was the site of an Iron Age oppidum, a Carolingian fortress, and during the Cathar period one of the most powerful castles of the Foix region, Montréal-de-Sos. Under the castle remains is a cave with two exits – or an entrance and a different exit. Such caves were used for initiation rituals in Cathar times.
The Cathar castle of Montsegur sits on top of a limestone peak (or pog in Occitan) at around 3000 feet. Here several hundred Cathars held out for 10 months against the besieging French army of over 6,000 men in 1243-44.