Machu Picchu

The ancient Incan citadel of Machu Picchu was rediscovered by an American archaeologist  in 1911. Perched on the eastern slope of the Peruvian Andes, the complex was built about 500 years ago, at the height of the Inca Empire. The city is made up of about 200 buildings, including temples, houses, and baths, and it’s roughly divided into an agricultural sector and an urban sector. Its many levels are connected by 3,000 steps, and there are sophisticated irrigation channels and fountains to distribute water.

One secret to the site’s preservation is its terrace system. The terraces provided ample places to grow crops, and they also helped the city cope with the heavy annual rainfall by providing a drainage system. The bottom layer of each terrace consisted of the stone bits that were chipped away during construction of the buildings. On top of that layer were smaller stone chips, and sand, and then topsoil. Excess water could drain down through these layers and be channeled away; without the terraces, mudslides would have carried Machu Picchu down the mountain long ago. The terraces also provide some protection against invasion, as their structure slows down any enemy’s progress toward the mountaintop.

It’s believed that Machu Picchu was built to be a resort or estate for Incan nobility, although it may also have been a religious site. It’s not clear why the Incans left, though, because there’s no evidence that Spanish conquerors ever found the site.

The so-called lost city was never lost to the locals, but Bingham was one of the first outsiders to see it. And it’s certainly no secret these days — hundreds of thousands of people visit Machu Picchu every year. It’s one of the largest tourist attractions in South America, and all the traffic and nearby construction is taking a toll on the site.