Machu Picchu is a fifteenth-century Inca citadel perched high on a mountain ridge in the Andes of Peru, around 2,400 metres above sea level. Famous for its dramatic setting, its finely crafted stonework, and the mystery of its purpose, it is the best-known symbol of the Inca civilisation and one of the most celebrated archaeological sites in the world.

Machu Picchu sits on a saddle between two peaks, surrounded by steep slopes that plunge to the Urubamba River far below, often wreathed in cloud. The site contains temples, palaces, houses, plazas, and storehouses, laid out with a sophisticated understanding of the landscape, water, and the sky.

The Inca built Machu Picchu without mortar, fitting blocks of stone together so precisely that a knife blade cannot be slipped between them, a technique that has helped the structures survive centuries of earthquakes. The finest stonework was reserved for the most sacred buildings, where huge, irregular blocks interlock like a puzzle.

The fine stonework of Machu Picchu's buildings, fitted together without mortar. Credit: Diego Delso (CC BY-SA 4.0).
The fine stonework of Machu Picchu's buildings, fitted together without mortar. Credit: Diego Delso (CC BY-SA 4.0).

Among the most striking features of Machu Picchu are its agricultural terraces, the andenes, which step down the steep mountainsides. These terraces did more than create flat ground for crops: they controlled erosion, managed the heavy rainfall, and helped stabilise the slopes against landslides.

The agricultural terraces, the andenes, that step down Machu Picchu's slopes, controlling erosion and water. Credit: F Delventhal (CC BY 2.0).
The agricultural terraces, the andenes, that step down Machu Picchu's slopes, controlling erosion and water. Credit: F Delventhal (CC BY 2.0).

Combined with an ingenious system of channels and fountains that carried fresh water through the site, the terraces reveal a society with deep practical mastery of building in a difficult, vertical world. A spring on the mountainside was tapped and led through stone conduits to a chain of fountains, supplying the city with clean water year-round.

Machu Picchu was probably built as an estate for the Inca ruler Pachacuti in the mid-fifteenth century, a royal retreat as much as a town. It was abandoned around the time of the Spanish conquest, though, crucially, the Spanish never found it, sparing it the looting and destruction visited on many other Inca sites.

Known to local people but unknown to the wider world, Machu Picchu was brought to international attention in 1911 by the American explorer Hiram Bingham. Its remote location had left it remarkably well preserved, and the photographs Bingham took astonished the world.

One of the first photographs of Machu Picchu, taken after Hiram Bingham brought it to world attention in 1911. Credit: Hiram Bingham III (Public domain).
One of the first photographs of Machu Picchu, taken after Hiram Bingham brought it to world attention in 1911. Credit: Hiram Bingham III (Public domain).

Today Machu Picchu is a UNESCO World Heritage Site, one of the New Seven Wonders of the World, and Peru's most famous attraction, drawing huge numbers of visitors along the Inca trails that lead to it. That popularity is also a threat: the strain of mass tourism on a fragile mountain site has led authorities to limit visitor numbers and routes in order to protect it for the future.