Château de Thomas II

At the southern end of the Lac du Bourget, the château de Thomas II was built on land acquired in 1248 by Thomas II of Savoy, brother of Count Amédée IV. A hunting rendezvous and lakeside residence of the counts of Savoy, it was almost entirely destroyed by fire. Bought back by the commune, it was classified Monument historique on 21 March 1983.

Today's visit comes in two parts: the castle's inner courtyard is freely accessible, and the restored Tour de la Poterne houses a museum space giving the keys to the protected marshes of the lake's southern shore. The tower opens in July and August, Tuesday to Sunday, 14:00–18:00 — €2 per adult, €1 per child.

The tourist office also runs guided tours linking the priory church of Le Bourget-du-Lac to the château Thomas II, with the Fondation Facim. Around the ruins, the shore is a protected natural area explored on foot.

July-August to enter the Tour de la Poterne (Tuesday–Sunday, 14:00–18:00). The rest of the year, the courtyard stays open and the protected shoreline marshes can be walked.