Which Inca site in Peru is known as a 15th-century mountain citadel?

Machu Picchu is the 15th-century Inca mountain citadel in Peru.

The site stands about 2,430 metres above sea level in the Andes, on a ridge above the Urubamba Valley. Archaeologists generally associate its construction with the reign of the Inca ruler Pachacuti, who ruled during the 15th century.

Machu Picchu contains terraces, plazas, temples, residences and carefully fitted stone structures. Its exact purpose is debated, but researchers commonly describe it as a royal estate or sacred ceremonial centre rather than a conventional city.

The site was not known internationally until the 1911 expedition led by Hiram Bingham, although local people were aware of it. Machu Picchu became a UNESCO World Heritage Site in 1983 and is one of Peru’s most important cultural and tourist landmarks.