Machu Picchu

A visit to the "Lost City of the Incas" is not for the faint of heart, but it is often described as life-changing (once you acclimate to the altitude). While the four-day hike along the Inca Trail is challenging, arriving at the Peruvian site during sunrise is well worth the effort, according to past travelers. If you're not up for the trek, you can also hop on a tourist train to the mountain base for an easier route to the top.