Trail running in Chamonix–Mont-Blanc

Chamonix is the spiritual home of mountain ultra-running, and every August the Ultra-Trail du Mont-Blanc turns its streets into the finish line of the most coveted race in the sport.

The full loop circles the entire massif — 171 kilometres and roughly ten thousand metres of ascent through France, Italy and Switzerland — a distance most runners cover in the better part of two sleepless days.

But the valley is a runner's paradise year-round, threaded with waymarked balcony trails that hang high above the town with the glaciers and the Mont Blanc skyline in constant view.

Whether you are chasing a UTMB place or simply running the Grand Balcon on a summer morning, this is trail running at its most spectacular and most serious.

Steep, sustained mountain trails with enormous vertical gain and loss — this is running that involves long powered-hiking climbs and technical rocky descents, not flat cruising.

The famous balcony routes give runnable high traverses with huge views, while the full UTMB course strings together pass after alpine pass, much of it run through the night in cold, changeable weather.

Expect thin air on the cols, exposed sections, and conditions that swing from hot valley floors to freezing ridgelines within hours. Even day outings demand navigation, layers and food.

The rewards are immediate: few places let you run for hours with 4,000-metre peaks and tumbling glaciers filling the horizon the entire time.

For casual running, come June to September and start with the Grand Balcon Nord or Sud — accessible by lift, superbly waymarked, and forgiving if you turn back. Carry a windproof layer, water and food even on short outings; mountain weather turns fast.

For the UTMB itself, entry is hard-won: you accumulate qualifying performances through the UTMB Index and then enter a lottery, so plan a year or more ahead and train specifically for relentless vertical.

Build up your climbing legs on long hilly runs, practise eating on the move, and rehearse using poles. Whatever your goal, respect the altitude and the exposure — treat these as mountain days that happen to be run rather than road races.