The climb from Puebla de Lillo to the Puerto de San Isidro is pretty easy (224 climb effort points). The first 4 kilometers are almost horizontal (maximum 2%). These are followed by the hardest part of the ascent (2.5 kilometers at a maximum of 7%), a descent (68 meters in altitude) and finally by another 6 kilometers that climb gently (0-6%). On this side of the pass you are in the Castilla y León region, where there is much less rainfall than on the other side of the pass in Asturias. The landscape with its rugged, barren mountains is beautiful and almost uninhabited. Unfortunately, a ski area mars the last part of the climb.