Machu Picchu lies in the Andes. Its buildings, terraces, and drainage structures respond to the mountain environment, while its stonework displays the technical characteristics of Inca civilization.
Expeditions in the early 20th century brought international attention to the site, but local residents had already known about it. It cannot simply be described as a city unknown to everyone.
Agricultural activity
Much of the farming carried out at Machu Picchu was done on its andenes (artificial terraces). These terraces were a work of considerable engineering, built to ensure drainage and soil fertility while also protecting the mountain itself from erosion and landslides. However, the terraces were not perfect, as studies of the land show that there were landslides that happened during the construction of Machu Picchu. Still visible are places where the terraces were shifted by landslides and then stabilized by the Inca as they continued to build around the area. The terraces also facilitated the management of water for agriculture, increasing crop yields, with maize likely being the main crop due to its ceremonial importance, alongside possible cultivation of potatoes.
However, terrace farming area makes up only about 4.9 ha (12 acres) of land, and a study of the soil around the terraces showed that what was grown there was mostly corn and potatoes, which was not enough to support more than 750 people living at Machu Picchu. This explains why studies done on the food that the Inca ate at Machu Picchu suggest it was imported from the surrounding valleys and farther afield.
Layout
The site is divided into two main sectors: an agricultural sector to the southeast composed of terraces (andenes), and an urban sector to the northeast containing residences, places of worship, and warehouses. The urban sector is further split into an upper town (Hanan) and a lower town (Hurin).
The Hanan contains the Sacred Plaza (Plaza Sagrada), a courtyard complex incorporating the Main Temple and the Temple of the Three Windows and capped by a pyramid-like stone platform on which the Intihuatana stands. In contrast, the Hurin is marked by trapezoidal doorways and small rectangular kanchas, including three large, symmetrically arranged kanchas with housing and workshops overlooking the Main Square (Plaza Principal), and a large single-entrance building interpreted as an Acllahuasi; nearby is the Temple of the Condor, which includes ritual caves and a large carved stone often interpreted as a condor.
The architecture is adapted to the mountains. Approximately 200 buildings are arranged on wide parallel terraces around an east–west central square. The various compounds, called kanchas, are long and narrow in order to exploit the terrain. Sophisticated channeling systems provided irrigation for the fields. Stone stairways set in the walls allowed access to the different levels across the site. The eastern section of the city was probably residential. The western section, separated by the square, was for religious and ceremonial purposes. This section contains the Torreón, the massive tower which may have been used as an observatory.
Located in the urban sector are the primary archaeological treasures and tourist attractions: the Intihuatana, the Temple of the Sun, and the Temple of the Three Windows.
The Popular District, or Residential District, is the place where the lower-class people live. It includes storage buildings and simple houses. The Guardian's house is a three-sided building, with one of its long sides opening onto the Terrace of the Ceremonial Rock. The three-sided style of Inca architecture is known as the wayrona style. In 2005 and 2009, the University of Arkansas made detailed laser scans of the entire site and of the ruins at the top of the adjacent Huayna Picchu mountain. The scan data is available online for research purposes.