Machu Picchu: the mysteries solved, the ones still open, and how the Incas built it

Architecture · 4 September 2026

Machu Picchu was built by the Inca emperor Pachacuti as a royal estate around 1420 to 1450, on a ridge 7,970 feet (2,430 m) above the Urubamba river, 50 miles (80 km) northwest of Cusco. It was not a lost city in the sense of a forgotten capital: it housed a few hundred people, the emperor's household, priests, craftsmen and farmers from across the empire, and it was abandoned within about a century, before or just after the Spanish conquest of 1532. The Spanish never reached it; local farmers always knew it; Hiram Bingham of Yale brought it to the world in 1911. Most of what was called mystery a century ago has been answered by excavation, radiocarbon dating and the study of the bones Bingham took to Yale. Below: what is settled about the builders and purpose, the engineering that keeps it standing, what remains unknown, and a separate section for the theories.

Who built it and why: solved

Spanish documents from the 1560s, found in the 1980s, record a lawsuit by Pachacuti's descendants over lands including "Picchu", listed among the estates the ninth emperor built for himself after conquering the region. That fits the archaeology: the site's style belongs to Pachacuti's reign, and an Inca royal estate was a private country residence, a place to entertain nobles, receive tribute and worship, worked by retainers brought from elsewhere. In 2021 radiocarbon dating of 26 human burials by Richard Burger's team put the occupation at about 1420 to 1530, twenty years earlier than the chronicles suggested for Pachacuti's rise, which means the Inca expansion itself began earlier than the Spanish-era histories say. Machu Picchu overview.

Who lived there: solved by the bones

Bingham excavated 174 burials and shipped the remains to Yale, where they were studied for a century before their return to Peru in 2011. They are not, as he thought, mostly women: the sex ratio is roughly even, and the "Virgins of the Sun" story came from a misreading of small female skeletons. Isotopes in the teeth and bones show the residents grew up in many regions of the empire, from the coast to Lake Titicaca, ate maize-heavy diets, and showed few signs of hard labour or violence; they were the yanacona, the permanent retainers of a royal household. A 2023 DNA study confirmed the diversity, with ancestries from across the Andes and the Amazon. The elite who visited left almost no burials: they were buried in Cusco.

How it was built: the engineering

• The site. The ridge sits between two faults and gets about 80 inches (2,000 mm) of rain a year; without engineering it would wash into the river. The engineer Kenneth Wright showed that about 60 percent of the construction is underground: foundations, terrace fill and drainage.
• Terraces. Around 700 terraces, each with a wall of stone, a base layer of large rock, then gravel, then sand, then topsoil carried up from the valley, so that rain drains through rather than saturating the slope. They grew maize and potatoes and held the mountain together.
• Drains. About 130 drain outlets have been counted in the walls, and a central drain runs under the main plaza. A spring on the north slope feeds a 2,457-foot (749 m) canal with a gradient of about 3 percent to a chain of 16 stone fountains running down through the city, the first at the emperor's residence.
• The stone. White granite quarried on the site; a field of half-worked boulders lies at the west edge. Blocks were split along natural cracks with wooden wedges and bronze bars, shaped with harder hammerstones, and dragged and levered into place with ramps and ropes. There are no wheels, no iron and no draught animals in Inca building.
• The walls. The finest buildings, the Temple of the Sun, the Principal Temple and the emperor's quarters, are ashlar: blocks ground to fit their neighbours so exactly that a knife blade will not enter the joint, with slightly inward-leaning walls and trapezoidal doors and windows that resist earthquakes by rocking and settling back. The 1950 and 2007 earthquakes did not move them.

What the buildings were for

The Intihuatana, a carved granite outcrop at the highest point, casts no shadow at noon on the equinoxes and is aligned to the peaks around; its name, "hitching post of the sun", is a modern coinage, and its use for tracking the sun is likely but not proven. The Temple of the Sun, the only curved building, has a window aligned to the June solstice sunrise, confirmed by measurement. The Temple of the Three Windows looks onto the plaza; the Temple of the Condor incorporates a rock shaped like a bird; the residential sectors east of the plaza held the retainers. About 200 buildings in all, most single-room houses with thatched roofs.

Why the Spanish never found it

Because it was already empty or nearly so, and because it was a private estate rather than a town on a road. When the Spanish took Cusco in 1533 the Inca state collapsed, the royal households that supported estates like Machu Picchu lost their income, and epidemics of European disease reached the Andes before the conquerors did. The last Inca rulers retreated to Vilcabamba, further down the valley, which the Spanish did reach and destroy in 1572. Machu Picchu appears in the 1560s land documents as a place name, and in 1874 on a map by the German engineer Herman Göhring; farmers were living on the terraces when Bingham arrived, and a local boy led him up.

What is still unknown

• Its name. "Machu Picchu" is the name of the mountain ("old peak"); a 2022 study of Bingham's notes and colonial sources suggests the Incas called the site Huayna Picchu, after the smaller peak, or simply Picchu.
• Whether it was abandoned before or after 1532. The latest burials date to about 1530; the absence of Spanish objects suggests the site was empty by the time any could arrive.
• What happened to the gold. Bingham found almost no precious metal, and there is no record of any being taken. Either the household removed it, or a royal estate simply had less than the legends assume.
• The precise purpose of the Intihuatana and several rock shrines. The Incas wrote nothing down; the readings are inferred from alignments and from what chroniclers said about similar stones in Cusco.

Versions and theories

Everything below is a version, not a fact. These are the claims that appear in search next to "Machu Picchu mystery", each with who made it and what the evidence says.

The last refuge of the Incas

Version. Bingham's first theory: he had found Vilcabamba, the city where the last Inca rulers held out until 1572. Reply. Vilcabamba was identified in 1964 at Espíritu Pampa, further into the jungle, where Spanish-period objects were found. Machu Picchu has none.

A convent of the Virgins of the Sun

Version. Bingham's second theory, based on the skeletons he believed were mostly female. Reply. Re-examination at Yale found the sexes roughly equal; the story was withdrawn by the university itself.

The birthplace of the Incas, Tampu Tocco

Version. Bingham's third theory, that the Temple of the Three Windows was the cave of origin in Inca myth. Reply. The site dates to the empire's height, not its beginnings; the origin cave in the chronicles is at Pacaritambo, south of Cusco.

Older than the Incas

Version. The fine ashlar walls were built by an earlier civilization and the Incas only reused the site. Reply. Every radiocarbon date, every pot and every burial is Inca of the 15th and early 16th centuries, and the same masonry is found in Cusco in buildings the chroniclers saw the Incas build.

A lost city found by chance

Version. Bingham "discovered" a site unknown to anyone. Reply. Farmers were living there, the name was on an 1874 map, and at least two other outsiders, Augusto Berns in the 1860s and Agustín Lizárraga in 1902, had been there; Lizárraga's name was written in charcoal on a temple wall when Bingham arrived.

Aliens, Atlantis and energy vortices

Version. The usual claims about mortarless walls and mountain sites. Reply. The quarry with half-finished blocks is inside the site, the tool marks are visible, and the same construction was watched and described by Spanish chroniclers in Cusco within living memory of the builders.

What is in the archive

Machu Picchu sits in the Ancient temples of the world collection with the other Andean sites: Coricancha, the Inca Temple of the Sun in Cusco, Tiwanaku on the Bolivian altiplano, Chavín de Huántar and Caral, the oldest city of the Americas. For Mexico's greatest city see who built Teotihuacan.

Open the sections: ancient temples of the world, buildings by style, all articles.