I am shown at the Overlook of the Birds on the formidable Choquequirao trail in Peru. Thousands of feet below, the Apurímac River carves its way through the Andes Mountains. The trek is considered one of the most difficult in South America: It makes its way through several indigenous Quechua villages, eventually leading to Inca ruins high in a cloud forest. Click the above image to enlarge, click to view my high-resolution photo gallery, or click to read my travel guide “How to Hike to Choquequirao.”