On an annual basis, a sports event takes place in the Jungfrau area of Switzerland. The Inferno covers different challenges including a half-marathon, a thriathlon and a fun triathlon. The half-marathon, shown in this photo, is a 21km run with a more than 2000m height difference running from Lauterbrunnen (795m above sea level) to the top of Schilthorn (2970m above sealevel). The race passes through Murren, where this photo was taken.
The triathlon also passes by the same location and includes 3.1km swimming on Thuner lake, 97km of road bking, 30km of mountain biking and 25km of running up Schilthorn similar to the half-marathon.
More information about he event can be found here. This specific photo was taken during the 2012 event on a very warm day.