The Swiss Irontrail is a Graubünden mountain trail series centered on a 200.3 km ultra that starts and finishes in Davos Platz. The T201 race climbs and descends 11,440 m, with runners given 64 hours to complete the loop. The program also features shorter ultras of 124.7 km and 90.3 km, a 42.3 km mountain marathon, two mountain half-marathons, and a 20 km trail with 800 m of climbing. The series was created by the organizers of the Swiss Alpine Marathon and is described in its own material as the longest and toughest ultramarathon in the Alps.
The T201 makes a large circuit through Davos, Bergün, the Engadin, Savognin, Lenzerheide, Arosa, and back to Davos Platz. Its high point is Fuorcla Surlej at 2,755 m, with the Bernina group in view. The route also uses locations such as Sertigpass, Kesch-Hütte, Muottas Muragl, Pontresina, Sils Maria, Maloja, Alp Flix, Weisshorn, and Strelapass. The shorter races use parts of that mountain network: the T121 bypasses the Bergün–Engadin–Savognin loop, the T91 runs from Bergün to Davos, and the T41 goes from Davos to Arosa and back. Course changes mean old winning times are difficult to compare directly.