For the full Monty Python medieval vibe, tackle the steep 20-minute climb to the ruins of this hilltop fortress, 32km east of Foix (and don't forget to bring your own water). It’s the westernmost of the string of Cathar castles stretching across into Languedoc; the original castle was razed to rubble after the siege, and the present-day ruins largely date from the 17th century.
It was here, in 1242, that the Cathars suffered their heaviest defeat; the castle fell after a gruelling nine-month siege, and 220 of the defenders were burnt alive when they refused to renounce their faith. A local legend claims that the Holy Grail was smuggled out of the castle in the days before the final battle. Tickets also grant admission to the historical museum in the nearby village of Montségur.