Rue des Châteaux climbs to a parking area in the groove between the twin castles of Sion. From here, paths divide up the dry, scrubby hillsides – left (north) to Tourbillon, right (south) to Valère.

Château de Valère is the more interesting of the two, and the more complete. The hike up brings you past the tiny Chapelle de Tous-les-Saints (dating from 1310 but unfortunately kept locked) and massive Roman foundation walls to the castle-church. As it stands, the château dates from the thirteenth century, but elements survive of earlier buildings, and the whole thing may well stand on the ruins of a Roman temple. A climb up rickety stairs brings you into the church interior (Tues–Sat 10am–noon & 2–6pm, Sun 2–6pm; Fr.3), where the most notable feature, high on the back wall, is the oldest playable organ in the world, dating from 1390. It’s still in use, played every Saturday during July and August as part of the International Festival of Ancient Music.

The Château de Tourbillon on the opposite hill dates from 1294, but was ruined by fire in 1788 and today, aside from the external walls, little is left. These days, it’s open for scramblings and yields excellent views along the valley and over the town (mid-March to mid-Nov Tues–Sun 10am–6pm; free).