The Tour du Castella crowns the rocky outcrop above the old town. It is all that remains of the medieval castle that once controlled the Ariège valley — a single stone tower, blown up after the Wars of Religion and left as a marker on the skyline.
A short, steep path climbs from the streets below to the foot of the tower. The reward is a clean view down the valley towards Foix and up into the Pyrenees, with the river curling around the old houses below. Half an hour is enough; combine it with a wander through the medieval lanes around the Place Garrigou.