Introduction
The Incas started building the estate around AD 1400 but it was abandoned as an official site for the Inca rulers a century later at the time of the Spanish conquest of the Inca Empire. Although known locally, it was unknown to the outside world before being brought to international attention in 1911 by the American historian Hiram Bingham. Since then, Machu Picchu has become an important tourist attraction.
The ruins of Machu Picchu are divided into two main sections known as the Urban and Agricultural Sectors, divided by a wall. The Agricultural Sector is further subdivided into Upper and Lower sectors, while the Urban Sector is split into East and West sectors, separated by wide plazas.
The central buildings of Machu Picchu use the classical Inca architectural style of polished dry-stone walls of regular shape. The Incas were masters of this technique, called ashlar, in which blocks of stone are cut to fit together tightly without mortar. The Incas were among the best stone masons the world has seen, and many junctions in the central city are so perfect that it is said not even a blade of grass fits between the stones.
Some Inca buildings were constructed using mortar, but by Inca standards this was quick, shoddy construction, and was not used in the building of important structures. Peru is a highly seismic land, and mortar-free construction was more earthquake-resistant than using mortar. The stones of the dry-stone walls built by the Incas can move slightly and resettle without the walls collapsing.
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Machu Picchu, Peru 
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