The first photograph upon discovery of Machu Picchu, 1911

In the summer of 1911, American archaeologist Hiram Bingham arrived in Peru with a small team of explorers, hoping to find Vilcabamba, the last Inca citadel to fall into the hands of the Spanish.

Traveling on foot and by mule, Bingham and his team made their way from Cuzco to the Urubamba Valley, where a local farmer told them of some ruins located on a nearby mountain peak. The farmer called the mountain Machu Picchu, which translates to "old peak" in the native Quechua language.

Bingham and his team made a six-day trek with excavators and camera equipment from the city of Cuzco to the city of Aguas Calientes, where they inquired at an inn about local ruin sites.

The innkeeper tells Bingham about a large complex on the hilltop that towers over the town. Bingham paid the innkeeper to guide him.

Halfway up a steep, forested hill, Bingham's guide stopped and instructed a boy to lead the American the rest of the way. When they reached the site of the ruins, Bingham found himself on a hill between two jagged peaks, surrounded by snow-covered mountains in the distance, rising 2,000 feet (610 m) above the raging Urubamba River.

The jungle had swallowed the entire site, but Bingham could make out several stone-covered terraces and walls made of carved granite stones, proving that a city had once stood on this rugged, remote rock.

Bingham later wrote that "Machu Picchu may prove to be the greatest and most important ruin discovered in South America since the days of the Spanish conquest".

Bingham set up his tripod and camera that day and spent the afternoon taking photographs. Over the next several months, he and his team cleared the forest of ruins, uncovering exquisitely constructed houses, temples, staircases, and terraces.

Archaeological evidence shows that people practiced agriculture in Urubamba and adjacent valleys as early as 760 BC. Between 1300 and 1500 AD, the Kingdom of Cuzco grew into a city-state, beginning with the government of Manco Capac.

The Vilcabamba region came under Inca control in 1440 during a campaign by the 9th Inca king Pachucatepec. This was one of the first stages of territorial expansion in what was to become the Tahuantinsuyo Empire.

According to scholars, Machu Picchu was a royal estate built around 1450 for the Inca king Pachacutec. Others speculate that the Inca city was a sacred center where the great political, religious, and economic minds of the Inca Empire gathered.

Machu Picchu had a population of between 300–1000 inhabitants and consisted mostly of members of the Pachacutec clan, religious elites, and highly specialized artisans recruited from across the empire, called yanaconas.

When Bingham found the ruins of Machu Picchu he found a treasure trove of artifacts, which he took with him to Yale University, including mummies, bones, ceramics, and precious metals. The Peruvian government has long requested the university to return these objects, which are estimated to number more than 40,000.

The most important structures of Machu Picchu are the Temple of the Sun (also known as Torreon), the Temple of the Three Windows, the Temple of the Condor, and the Intihuatana Stone.

The Intihuatana Stone (meaning 'hitching post of the sun') was an astronomical observational instrument used to determine the exact duration for various festivals and ceremonies of importance in the Inca religion.

The site is spread over 80,000 acres (32,500 ha) and is divided into an urban area and an agricultural area. It is estimated that 60% of the construction was underground, including deep building foundations and crushed rock for drainage.

The urban area consisted of the upper part where the royals lived and temples were built, and the lower part for workers' quarters and warehouses.