The race sets off from Pas de la Case, a commune on the Andorran/French border. Effectually, the riders descend the Col de Puymorens in the first kilometres, a pass they climbed in the stage before the rest day.
The route continues to descend, albeit false flat, and moves through Ax-les-Thermes and Tarascon-sur-Ariège before the first climb of the day appears after approximately 70 kilometres. The Col de Port is 17 kilometres long and slopes at 4.6%.
Up next is the Col de la Core, which is an ascent of 14 kilometer at 6,3%. The route then continues onto the infamous Col de Portet d’Aspet. The 5.4 kilometres climb at 7.1% serves its hardest sections in the second part. The last 1.4 kilometres go up at almost 10%.
In the descent the riders pass the monument in the memory of Fabio Casartelli, who crashed at that spot in the 1995 Tour de France. The Olympic champion of 1992 lost consciousness and his injuries proved to be fatal.
The summit of the Portet d’Aspet is 30 kilometres away from the finish line in Saint-Gaudens. After the descent the riders continue onto the flat, slightly downhill, until a 1 kilometre climb at 5% could turn out to be decisive in terms of the stage win.
The first three riders on the line gain time bonuses of 10, 6 and 4 seconds.
The 16th stage of the Tour de France starts at 13.05 and the race is expected to finish around 17.35 – both are local times (CEST).