The path leaves El Portillo on the east side, goes up a few meters along a channel and enters the north side. If the mountain has snow, this section is dangerous because the cold and shady conditions keep the path icy and the fall is fatal; crampons and ice axes would be essential. The alternative is to climb directly along the channel on the east face, with less slope, sunnier and direct to the summit of San Millán (2,131 m), also called El Torruco. At the top there is a small circular stone tower adorned with a metal house and other festival motifs left by mountaineers. The southern slope of the mountain is a large mass of gentle slopes with no remains of glacial activity towards the valley of the Arlanzón River. The descent continues along the west face, enjoying extraordinary views of the Urbión River valley and the glacial cirque where the San Millán lagoon appears half frozen.