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. 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.
Inca walls had numerous design details that helped protect them against collapsing in an earthquake. Doors and windows are trapezoidal and tilt inward from bottom to top; corners usually are rounded; inside corners often incline slightly into the rooms; and "L"-shaped blocks often were used to tie outside corners of the structure together. The Incas never used the wheel in any practical manner. According to archaeologists, the urban sector of Machu Picchu was divided into three great districts: the Sacred District, the Popular District to the south, and the District of the Priests and the Nobility.
As part of their road system, the Incas built a road to the Machu Picchu region. Today, tens of thousands of tourists walk the Inca Trail to visit Machu Picchu each year. The people of Machu Picchu were connected to long-distance trade, as shown by non-local artifacts found at the site. In the 1970s, Burger and Asaro determined that these obsidian samples were from the Titicaca or Chivay obsidian source, and that the samples from Machu Picchu showed long-distance transport of this obsidian type in pre-Hispanic Peru.
The three-sided style of Inca architecture is known as the wayrona style.
Machu Picchu is a UNESCO World Heritage Site. Since its discovery in 1911, a growing number of tourists visit Machu Picchu, reaching 400,000 in 2003. Many protested a plan to build a bridge to the site as well. UNESCO is considering putting Machu Picchu on its List of World Heritage in Danger.
In 2006 a Cusco-based company, Helicusco, sought to have tourist flights over Machu Picchu and initially received a license to do so, but the government quickly overturned the decision.
