K42 Series is an international off-road marathon circuits, more precisely races of trail running on paths immersed in the nature from the most different landscape contexts, where nature is always dominant. The race circuit started in 2009 in Argentina and now is in rapid extension in South America, Europe and Africa. K42 Series, together with K21 Series, has a large number of users and an international media coverage. Regarding the Italian K42, the race itinerary will traverse the most suggestive and demanding paths of the Terminillo’s massive mountain. The start and the finish line will be in Pian de’ Valli, the centre of the ski area of Rieti.