Reunion Island — Volcano Ultra Running in the Indian Ocean

The Island That Ultra Running Built

There are places that have trail running. Then there is Reunion Island, where trail running is practically a religion. This tiny French overseas territory — just 63 kilometers long and 45 wide — sits in the Indian Ocean east of Madagascar and packs more vertical terrain per square kilometer than almost anywhere on Earth. It is home to the Grand Raid, also known as the Diagonale des Fous (the Madmen’s Diagonal), one of the most grueling and prestigious ultra races in the world.

But you do not need to race 170 kilometers to appreciate what makes Reunion special. The island’s trail network covers over 900 kilometers, threading through volcanic landscapes, along knife-edge ridges, and into cirques so deep and remote that some villages inside them have no road access at all.

Piton de la Fournaise — Running on an Active Volcano

Piton de la Fournaise is one of the world’s most active volcanoes, erupting multiple times a year, and you can run on it. The trail from Pas de Bellecombe to the crater rim crosses a surreal moonscape of hardened lava flows in shades of black, red, and ochre. The ground crunches underfoot and steam vents hiss from fissures. It feels like another planet.

The out-and-back to the Formica Leo crater and Dolomieu summit covers about 11 kilometers with 500 meters of elevation change. It is not the biggest day on the island, but the landscape is so alien and compelling that it ranks among the most memorable runs you will ever do. Check eruption status before you go — the trail closes when the volcano is actively erupting, which happens more often than you might expect.

Reunion’s interior is dominated by three massive cirques — collapsed volcanic calderas surrounded by walls that rise over 1,000 meters. Each has its own character, and together they form the heart of the island’s trail running network.

Mafate is the wildcard. There are no roads into Mafate. The only way in or out is on foot or by helicopter. Villages like La Nouvelle and Marla exist in a kind of beautiful isolation, connected by trails that climb and descend relentlessly. Running through Mafate feels like stepping back in time, and the effort required to get there makes every view feel earned.

Cilaos is the athletic hub, home to many of the island’s top trail runners and the start of several classic routes. The trail up to Piton des Neiges, Reunion’s highest point at 3,071 meters, starts here. It is a pre-dawn start for most — you climb in the dark to reach the summit for sunrise, and the 360-degree view over the island and ocean is worth every step.

Salazie is the greenest and most accessible cirque, with waterfalls cascading down its walls and the picturesque village of Hell-Bourg at its center. The trails here are lush, steep, and often muddy — classic tropical mountain running.

The Diagonale des Fous — For the Truly Committed

The Grand Raid’s flagship event covers roughly 170 kilometers with over 10,000 meters of positive elevation gain, crossing the island from south to north through all three cirques and over the volcano. It regularly has a dropout rate over 40 percent. The race attracts elite ultra runners from around the world, but the real magic is in the community support — entire villages turn out to cheer runners through the night, offering food, music, and encouragement at every aid station.

Even if you never race it, training on these trails gives you a taste of what makes the Diagonale legendary. The terrain is relentless, the beauty is constant, and the sense of accomplishment after any significant run here is immense.

Your Indian Ocean Trail Running Base

Reunion combines French infrastructure and cuisine with tropical warmth and volcanic drama. The trails are well-marked, mountain huts and guesthouses provide shelter on multi-day routes, and the Creole food — a fusion of French, Indian, Chinese, and African flavors — is outstanding recovery fuel.

This island punches so far above its weight in the trail running world that it deserves a spot on every serious runner’s bucket list. Share your Reunion adventures with the ZealZag community and connect with athletes who understand that the best trails are the ones that push you to your limits.