The 27 km option at Grands Trails d'Auvergne is the Trail Du Lac Boucle, a short mountain-trail race run from the lake at Aubusson-d'Auvergne. The solo race measures about 25.34 km with 839 m of climbing, while the duo version is almost identical at about 25.36 km with 837 m of climbing.
Runners leave the lakeside and complete a single loop with approximately 800 m of elevation gain, making the race compact but not flat. The format offers a choice between covering the route alone or sharing the same distance as a pair, and both versions count toward the UTMB Index.