Tens of thousands of pilgrims crowd an Andean valley, with dancers in multi-layered skirts and musicians with drums and flutes performing non-stop over three days. The native melodies resound throughout a snow-capped mountain range long adored by the Quechua people.

Known as the Snow Star festival, the gathering is held every year shortly before the Christian feast of Corpus Christi and draws as many as 100,000 people to the Quispicanchis province in Peru's Cuzco region. It also coincides with the reappearance of the star cluster Pleiades in the Southern Hemisphere, signaling the abundance of the harvest season.

Inscribed on UNESCO'S Intangible Cultural Heritage list, the festival features a pilgrimage by local people to the sanctuary where a boulder features an image of Jesus Christ known as the Lord of Qoyllur Rit'i (pronounced KOL-yer REE-chee), or Snow Star in the Quechua language.

The sanctuary is in the Sinakara Valley at the base of the Qullqip'unqu mountain in the Andes. Parish churches in the area provide food for the pilgrims, who camp out in the valley.

The celebration mixing Roman Catholic and indigenous beliefs honors Jesus as well as the area's glacier, which is considered sacred among some indigenous people. While the native celebration is far older, the Christian part of the ritual stretches back to the 1700s, when Jesus is said to have appeared to a young shepherd in the form of another boy.

On the last night of the festival, men known as "ukukus" climb more than 4,500 meters (about 14,765 feet) in freezing temperatures up to the Qullqip'unqu mountain's glacier. They dress as half-bear, half-man creatures and carry crosses up the slope to spend the night at the top. They descend with their crosses as first rays of the morning sun spread across the mountain range and are met by groups of women and children.

The ukukus are organized into militaristic groups with strict rules overseen by a "corporal." When new recruits reach the glacier, each kneels before a cross and places their hands on the ice.

In recent years, the pilgrims have noted a decline in the size of the glacier because of warming trends. In hopes of preventing additional melting, the ukukus no longer use the large candles that were once common in the ritual. The ukukus also used to cut away ice cubes to bring down, but no longer do so.

Jose Luis Mamani, president of the Paucartambo, one of numerous "nations" making the pilgrimage, said members of his group "are very worried about the state of this sacred place."

Still, after praying to the Lord of Qoyllur Rit'i for health, peace and prosperity, the pilgrims head home with their hope intact and the expectation they will perform the ritual again next year.