RunThrough Interlaken Trails Festival June 2026

The RunThrough Interlaken Trails Festival is a trail running weekend in Interlaken, Switzerland, offering three race distances: 42k, 22k, and an Up & Down Race. The courses traverse the narrow land strip between Lake Thun and Lake Brienz before ascending into the terrain surrounding the Harderkulm. This event features mountain running with technical terrain, distinct from a flat road race. Participants will cross the Aare River and climb above Interlaken, gaining views of the Eiger, Mönch, and Jungfrau from the Harderkulm vicinity. The descents allow for faster running, though careful footing is still required. The 42k route extends into the Beatenberg valley, including sections alongside Lake Thun and through mountain river gorges. RunThrough, with established events in London and across the UK, is expanding its RT Trails series with this Swiss festival.