Steepest kilometer begins at km 3.3 (11.3%)
Climb beings in Ax-le-Thermes (population 1,244, 2012) and ends at Station de Ski Pyrenees Ax Domaines 8 kilometers up the road at an average grade of 8.2%. PJAMM will ride and document this climb in August, 2018 (we climbed, but did not document this challenging ride in 2013).
Wikipedia notes of this location:
“Ax 3 Domaines is a winter sports resort situated in the commune of Ax-les-Thermes, departement of Ariège, in France. Since 2001, the climb to the ski station has been used as a stage finish in the Tour de France cycle race.
On 6 July 2013, the eighth stage of the Tour de France finished in the resort at an altitude of 1,375 m (4,511 ft).” https://en.wikipedia.org/wiki/Ax_3_Domaines
The tour has visited Ax 3 Domaines 5 times beginning in 2001.