The Incas built the largest empire and dynasty of pre-Columbian America.[6] The Tahuantinsuyo which is derived from Quechua for "The Four United Regions" reached its greatest extension at the beginning of the 16th century. It dominated a territory that included (from north to south): Ecuador, part of Colombia, the northern half of Chile, and the north-west part of Argentina; and from east to west, from Bolivia to the Amazonian forests and Peru.
The empire originated from a tribe based in Cuzco, which became the capital. Pachacutec was the first ruler to considerably expand the boundaries of the Cuzco state. His offspring later ruled an empire by both violent and peaceful conquest.
In Cuzco, the royal city was created to resemble a Cougar; the head, the main royal structure, formed what is now known as Sacsayhuaman. The Empire's administrative, political, and military center was located in Cuzco. The empire was divided into four quarters: Chinchasuyo, Antisuyo, Contisuyo, and Collasuyo.
Quechua was the official language, imposed on the citizens. It was the language of a neighbouring tribe of the original tribe of the empire. Conquered populations tribes, kingdoms, states, and cities—were allowed to practice their own religions and lifestyles, but had to recognize Inca cultural practices as superior to their own. Inti, the sun god, was to be worshipped as one of the most important gods of the empire. His representation on earth was the Inca ("Emperor").
The Tahuantinsuyo was organized in dominions with a stratified society, in which the ruler was the Inca. It was also supported by an economy based on the collective property of the land. In fact, the Inca Empire was conceived like an ambitious and audacious civilizing project, based on a mythical thought, in which the harmony of the relationships between the human being, nature, and gods was truly essential.
Many interesting customs were observed, for example the extravagant feast of Inti Raymi which gave thanks to the God Sun, and the young women who were the Virgins of the Sun, sacrificial virgins devoted to the Inti. The empire, being quite large, also had an impressive transportation system of roads to all points of the empire called the Inca Trail, and chasquis, message carriers who relayed information from anywhere in the empire to Cuzco.

Machu Picchu (Quechua: Old Peak; sometimes called the "Lost City of the Incas") is a well-preserved pre-Columbian Inca ruin located on a high mountain ridge above the Urubamba Valley, about 70 km (44 mi) northwest of Cuzco. Elevation measurements vary depending on whether the data refers to the ruin or the extremity of the mountain; Machu Picchu tourist information reports the elevation as 2,350 m (7,711 ft). Forgotten for centuries by the outside world, although not by locals, it was brought back to international attention by Yale archaeologist Hiram Bingham III, who rediscovered it in 1911 and wrote a best-selling work about it. Peru is pursuing legal efforts to retrieve thousands of artifacts that Bingham removed from the site.
Although Machu Picchu is by far the most well-known internationally, Peru boasts many other sites where the modern visitor can see extensive and well-preserved ruins, remnants of the Inca-period and even older constructions. Much of the Inca architecture and stonework found at these sites continues to confound archaeologists. For example, at Sacsayhuaman, in Cuzco, the zig-zag-shaped walls are composed of massive boulders fitted very precisely to one another's irregular, angular shapes. No mortar holds them together, but nonetheless they have remained absolutely solid through the centuries, surviving earthquakes that flattened many of Cuzco's colonial constructions. Damage to the walls visible today was mainly inflicted during battles between the Spanish and the Inca, as well as later, in the colonial era. As Cuzco grew, Sacsayhuaman's walls were partially dismantled, the site becoming a convenient source of construction materials for the city's newer inhabitants. Today we not only do not know how these stones were shaped and smoothed, lifted on top of one another (they really are very massive) or fitted together by the Incas; we also don't know how they got the stones to the site in the first place. The stone used is not native to the area, and most likely came from mountains many miles away.

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