Port de Lers is a nice climb in the Ariège region of the Pyrenees. It has been used six times in the Tour de France, most recently on stage 15 in 2019. The climb from Val-de-Sos is the more challenging of the two sides, with irregular gradients making it difficult to settle into a comfortable rhythm. Much of the climb is in forest, with the scenery really opening up in the final 2-3km.