Lakako Lasterkaldia is a hilly race in Ossès. The long route is 22 km with 1100 m of climbing, and a shorter 14 km option is available for those not seeking the full mountain effort. Both races start in the morning, with the 14 km beginning before the 22 km. Entry fees are modest: 6 EUR for the shorter race and 23 EUR for the longer one.
The course suggests steep, local running rather than a flat road event. An earlier edition featured a 21 km race with 1300 m of elevation gain, plus a walking hike. LOKARRI ELKARTEA organizes the race, attracting local club runners like a group of 14 from SPUC LASTERKA. The name is also known in French as Course du Laka, linking it to the Laka area near Ossès.