Pont du Lancet
Pont du Lancet is a high mountain tunnel at an elevation of 2.057m (6,748ft) above the sea level, located in the Valais region of Switzerland.
The road to the tunnel is mostly asphalted with some gravel sections. It's very narrow. It starts from the Lac de Mauvoisin at 1.961m (6,433ft) above the sea level, with a long tunnel. Around 1.5 kilometres long, it’s lit and has occasional windows. When the tunnel ends, it exits well above the water and follows the length of the 5 kilometre long lake. The road continues a bit up to the the tunnel.
After the bridge, the road continues to the Cabane de Chanrion, at 2.471m (8,106ft) above the sea level. The road is only accessible in summer for people with special communal authorization.
Pic: http://jujunette-des-alpages.com/2012/09/12/suite-du-pont-du-jeune-genevois-9-et-10-septembre/