Alto de San Isidro
Alto de San Isidro is a high mountain pass at an elevation of 1.523m (4,996ft) above the sea level, located on the Asturias and Castile and Leon border, in northern Spain. The climb is pretty steep, with sections up to 11.4%.
The road to the summit is asphalted. It’s quite wide so it’s pretty safe. Located within the Redes Natural Park, the summit is also known as Puerto de San Isidro. The road conditions are pretty good as it’s well maintained due to the fact it’s the main road to the ski slopes. In winter it can be very cold though so make sure that you come suitably prepared. The road is called AS-253 in Asturias and LE-331 in Leon. It’s usually open throughout the year to enable access to the ski resort. The pass has been climbed by the Spanish Vuelta.
There are 2 routes to reach the summit. Starting from Cabañaquinta (AS-253 road), the ascent is 27km long. Over this distance the elevation gain is 1.111 meters. The average gradient is 4.1% with sections up to 11.4%. And starting from Puebla de Lillo (LE-331 road), the ascent is 14.7km long. Over this distance the elevation gain is 433 meters. The average gradient is 2.5% with sections up to 8.7%.