Lac du Bourget

The Lac du Bourget stretches 18 km, up to 3.5 km wide, 44.5 km² and 145 m deep at its deepest point, between the royal abbey of Hautecombe and the Grésine bay — the figures are the Savoie préfecture's. The tourist office presents it as 'France's largest natural lake', and 'the largest natural lake by volume' (3.6 billion m³); the préfecture itself qualifies the surface-area title in favour of Lac d'Hourtin (58.3 km²) in Gironde. Both wordings are reported as they stand. The surface also varies by source: 44.5 km² (préfecture) or 45 km² (tourist office).

Around its 40 km of shores: the beaches (all rated Excellente in the 2025 departmental bathing-water rankings), 13 marina zones per Grand Lac — the tourist office counts 14 —, cruises to Hautecombe and the Canal de Savières, and the V63 greenway along the east shore from Aix-les-Bains to Chambéry. The lake is a designated UNESCO biosphere reserve.

The shores and the greenway can be enjoyed all year. In summer the water can reach 28 °C per the tourist office, and the beaches are lifeguarded from 27 June to 30 August 2026 (1 to 7 pm for most; Le Bourget-du-Lac and Mottets from 10 am). Note: on the Grand Lac-managed beaches, dogs are not allowed in the summer season, even on a leash.