At the beginning of the trek, we weren't quite acclimatized to the altitude. While we meandered up this mountain to a glacial lake, the Peruvians with us were sprinting ahead, which was more than humbling.
Many of these fields were, until recently, covered with ice. The scope of the glacial retreat is just startling, you can literally see, and hear, huge chunks of ice disappearing throughout the mountains.
—Photographer Brent Stirton
Plan your own trip with our Adventure Guide to Peru's Camino Salcantay >>
See the feature story "Machu Picchu the Cool Way" in the November 2007 issue of National Geographic Adventure.
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