The enigma of Machu Picchu refers to the mystery and intrigue surrounding the purpose, construction, and history of the ancient Inca site located high in the Andes Mountains of Peru. Machu Picchu, often referred to as the "Lost City of the Incas," was built around the middle of the 15th century, during the reign of the Inca emperor Pachacuti.

This remarkable site, nestled on a mountain ridge 7,970 feet (2,430 meters) above sea level, features sophisticated dry-stone walls that fuse huge blocks together without the use of mortar. The complex includes temples, residences, terraces for agriculture, and intricate water channels, demonstrating the architectural and engineering prowess of the Inca civilization.

The exact purpose of Machu Picchu remains a subject of speculation and debate among historians and archaeologists. Some theories suggest that it was a royal estate or a retreat for Inca nobility, while others propose that it was a religious site or an astronomical observatory.

Machu Picchu was abandoned during the Spanish conquest in the 16th century, and it remained unknown to the outside world until its rediscovery by the American historian Hiram Bingham in 1911. Since then, it has become one of the most famous archaeological sites in the world and a symbol of the Inca civilization. In 1983, UNESCO designated Machu Picchu as a World Heritage Site, recognizing its cultural, historical, and architectural significance.