The abandoned Tunnel du Mortier in France

# Tunnel du Mortier: France's Haunting Mountain Passage

Tucked away in the Isère department of southeastern France, the Tunnel du Mortier sits at a dramatic 1,370 meters (4,494 feet) in the heart of the Auvergne-Rhône-Alpes region. This quirky piece of mountain infrastructure has quite the backstory.

Originally built back in 1911, the tunnel got a major makeover in 1968 for the Grenoble Winter Olympics. A plaque at the north entrance commemorates the upgrade, which was officially inaugurated on September 30th by Louis Verger. But here's where things get interesting: the road didn't last much longer.

In April 1992, a massive rockfall—roughly 20,000 cubic meters of rock—came crashing down just below the summit of the Buffe, destroying the access road and making the whole situation dangerously unstable. The kicker? This happened just a kilometer from another epic collapse in 1971 (50,000 cubic meters). Given the road's limited importance and the ongoing threat of more slides, authorities threw in the towel and closed it for good.

These days, the two-lane tunnel (all 500 meters of it) sees hikers and mountain bikers instead of cars. The first 100 meters are straightforward, but the middle section gets seriously dark—bring a light. The smooth interior is blessedly obstacle-free, though you'll spot a few rocks toward the Isère end where daylight returns.

The approach road, D218, is paved but narrow with brutal gradients hitting 12% on some sections. The southeastern side is still drivable up to the tunnel, but the northwestern side has completely collapsed. Beyond the tunnel, a massive rockslide blocks any further progress, though adventurous souls with proper caution can cross it to descend into the Vercors. A forest track was briefly developed in 2017, but a landslide during winter 2021-2022 shut that down too. Mother Nature clearly has the final say here.