This link provides a two-way connection between Yenne and Lac du Bourget, passing from one side of the Montagne de l'épine to the other, without the need for difficult ascents, thanks to the dedicated gallery of the Tunnel du Chat.
This link between the two sides of the Montagne de l'Epine allows you to discover two different sides of the mountain via the tunnel du Chat. On the Yenne side, you'll travel through the landscapes of the Billième vineyards, on shared roads and a section of greenway.
On the Bourget-du-lac side, coming from Chambéry or Aix-les-Bains on the V63, you'll skirt the lake and its harbour, and enjoy the breathtaking panorama of Lac du Bourget. The climb up to Bourdeau is not very long, but has some steep gradients.
From Le Bourget du Lac, take the Route du Lac / D14 to Bourdeau, then the D13 left to reach the tunnel road and the tunnel entrance. At the exit, turn right to reach the village of Billième, staying on the main road; at the entrance to Billième, turn left onto the D44, which will take you back down to Yenne via "Combes", "Bas Somont" and "Les Bernards". The itinerary is identical in the other direction. On entering or leaving Yenne, use the cycle paths to avoid the main road.