The document summarizes information about Machu Picchu, an ancient Inca city located in Peru. It was built in 1460 by the Inca emperor Pachacuti, and some believe it served as a retreat, religious sanctuary, or military stronghold. The city is located on mountain ridges between the Urubamba River valley and Machu Picchu mountain. It remains a popular tourist destination today that has faced challenges from overtourism, including landslides, erosion, and litter.