The Inca citadel of Machu Picchu in Peru is one of the world's most spectacular ruins.  Houses, temples, staircases and agricultural terraces were built high among rugged and forested mountains with distant show-covered Andean peaks providing a backdrop.  Far below, the rapids of the Urubamba river loop around the site.

This photo shows how Machu Picchu is divided by a grassy central plaza.  To the left is the upper urban area that contains the most interesting and important buildings in Machu Picchu, including those with the most religious significance.  To the right and extending downhill is the more mundane lower urban area.