Monday, August 8, 2011



This article has two parts: the first one was devoted to urban planning architecture of Machu Picchu and its relationship with the landscape . This post reviews aspects of its engineering, geological, construction and agricultural and hydraulic planning .


Federico Kauffman Doig has argued in a series of papers about the difficulties that the ancient Peruvians had to overcome in order to get to cover the share of food that their population growth demanded. Indeed, to the unfavorable conditions for agriculture in Peruvian territory (an arid coast, rough highlands and an almost impregnable jungle) frequent phenomena experienced in the Peruvian territory were added : earthquakes, droughts, El Niño, landslides, etc. Perhaps, suggests Kauffman, that was the reason for the higher-cultural development in this part of the continent, as the ancient Peruvians had to develop complex technologies and organized socio-religious societies that allowed a maximum benefit from the land, even in such adverse conditions.

Machu Piccu terraces. Step down into the abyss?. Photo courtesy of Bird on a Wire.

Understanding agricultural expansion as a key objective for the Incas, Kauffman suggests that Machu Picchu was "an important center of agricultural production management", based on the need to expand the agricultural frontier into the Amazon Andes. But the analysis performed by Kenneth R. paleohydrological Wright, would have led to the conclusion that the arable areas in Machu Picchu supplied only 55 people, so that food would have been brought from elsewhere. Kauffmann, based on studies of Ann Kendal, suggests that Machu Picchu would have been part of a series of agro-cultist centers such as Huiñayhuina or Intipata, located in the same region.

Throughout the city there are over 600 andenes or terraces, which were not only for agriculture but mainly served as wedges to prevent landslides. On average, the terraces were between 2 meters wide and 3.5 meters high, defined by a stone wall. Inside, layers of dirt and stone ensured a good runoff during heavy rainfall in the Amazon rainforest. The lower base was a stone fill that provided stability and easy flow of water. Above it was a layer of smaller stones, gravel and a layer of sand. Finally they were covered by fertile soil, which often reaches a thickness of one meter, and was probably brought from the valley at the bottom of the ravine.

3D Model of Machu Picchu


Located at the beginning of the citadel, in the southeast, the agricultural area is a group of terraces bordering the dry moat. According to archaeologist Luis Lumbreras, "more than a simple agricultural space, the agricultural sector submitted the provision of food to the demands of aesthetic values. Together with corn or coca, which the Incas very likely planted on those platforms, they also grew orchids and other colors and flavorings. "

Structure of a platform or terrace. Image courtesy of History Channel.

In the agricultural area there are some constructions:


The roofs of these staggered storehouses or colcas have been reconstructed by archaeologists to give an idea of how to Machu Picchu would have originally look like.

Colcas or warehouses to the income of the agricultural area. Photo courtesy of Fotolobo

Corrals for llamas
As many organic remains of llamas have been found around, it is believed that these were rectangular enclosures with narrow inlets where the animals were confined.

Photo courtesy of


Located high in the agricultural zone, it enjoys great views of the citadel. Nearby is a cemetery and a ceremonial rock.
Watchhouse. Photo courtesy of Lall


Renowned Brazilian geologist Rualdo Menegat offers an interesting interpretation of the role of faults in structuring the location and construction of the Inca cities in the landscape . Menegat based his hypothesis on the fact that faults are important sources of building material, they made easier to model the terrain and they contain plenty of aquifers.

Photo courtesy of Rualdo Menegat

Indeed, Machu Picchu has many faults and abundant rock fractures. The two main faults are called Machu Picchu and Huayna Picchu, which form a wedge-shaped block upon which the citadel sits on. This fault system determines that the topography of the sanctuary and its orientation can be identified by aligning the nearly vertical northeast side of Machu Picchu with linear sections of the Urubamba River along the southeast flank of the Putucusi mountain.

Topography and fault lines in the industry.
Source: K.Wright

Menegat suggests that the Incas had a wide knowledge of the geological and geomorphological elements of the landscape, both at a macro scale (in order to put cities in the safe areas at the top of the mountains, to analyze the runoff, and to organize the city according to topographical areas) and a micro scale (the stone carving understanding the direction of the same geological fractures).
He further suggests that instead of using a Euclidean geometry, the Incas used a "petrometry" ie, following the logic of the stone. For example, in the Temple of the 3 Windows, the stones of the base have more irregular patterns on top.

Temple of the Three Windows (the two lateral niches were filled later). Note how the arrangement of stone blocks is due to their tectonics and not to a particular geometry.


The Apus or mountain gods were deeply worshipped by the Incas, especially if they had any figurative reference that evoked some divine being (such is the case of Pinkuylluna mountain in Ollantaytambo ). In that sense, the Huayna Picchu outline has been associated to a human profile, but honestly I found this reference only in popular tradition rather than among the studies of researchers.

Inca Profile at Machu Picchu, where the nose would be the Huayna Picchu and the chin would be Uña Huayna Picchu. I have often found that image, artistically distorted for tourists, so this is a real photo, taken at dawn, when shadows more clearly contrast the profile of the mountain. Photo courtesy of Eugene.

However I think the references to the surrounding mountains during Machu Picchu's planning, form a more complex system that encompasses the snowcapped mountain ranges and the surrounding countryside. In that sense, the researcher Lee Anne Hurt, Assistant in charge of the American Art Gallery of Old Museum of Fine Arts in Virginia, in his doctoral thesis carried out an interesting study about the meaning of the huacas as links between the mountains or apus and the city, used as an important element in the planning of Machu Picchu. Hurt documented, in a comprehensive and systematic way, 122 huacas in the various sectors of the citadel, demonstrating the sacred character as well as the builders meticulous planning.

Sacred rock showing its alignment with Mount Yanantin. Photo courtesy LAHurt

Huacas or sacred rocks, were understood as metaphysical connections between the supernatural world and humans, and they have been documented by various writers and authors, among them, the late 15th century graphs by Guaman Poma de Ayala and the Huarochiri Manuscript.

Inca knees, adoring a huaca.Image by Huaman Poma de Ayala

Based on these sources and a detailed field work, Hurt examined the role that huacas had as references in the mountain environment, studying the relationship between observer-huaca-landscape from different positions: standing, sitting and kneeling, discovering different visual relationships in each of them. In that sense, the huacas define a sacred place (the site at that they point) a profane place (the place they turn their backs at) and a ritual, which is in between the two of them.

Different perceptions of the same huaca with the landscape: A) Standing B) on one's knees. The visual relationship and mimicry of the Putucusi mountain is clearer at kneeling. Photos courtesy of L.A. Hurt

Hurt categorizes huacas as "Mark" (when they have some alignment with a landscape element), "Chamber" (an enclosure), "Repository" (where it was stored or deposited something) "Embedded", "Locked" and "Autonomous "(when they were isolated).In some cases a huaca may belong to more than one category.
Hurt's merit is to understand Machu Picchu as part of a much larger landscape and also to account for subtleties and even choreographed rituals of local inhabitants. Moreover, her research provides a greater understanding of the role of huacas in Inca cosmology and emphasizes the sacred character of the citadel.


Before creating any settlement, it was essential to ensure a supply of drinking water. Fortunately, the geological fault system also favored that a spring would emerge on the northern side of the mountain at 2458 m, as the permeability allows the infiltration of rainwater, which arise in this spring, providing a source of perennial water for the city.

With this purpose the Incas created a system of collectors consisting of a 14.6 m long and 1.4 m high stone wall. Water seeps through the wall and flows into a stone trench about 0.8 m wide. A fountain flows into the canal about 80 m east of the main fountain. Water runs along a 749 m long, 10 to 12 cm wide , 10 to 16 cm deep canal with a 3% slope and a capacity of 300 l-min. According to the Peruvian archaeologist Alfredo Valencia and the American engineer Kenneth Wright, the design of the canal determined the location of the residence of the emperor and the general layout of the city.

But the fountains were not only utilitarian but also had a ceremonial role, since water was considered a deity given its importance in agriculture. 16 liturgical fountains or Pakcha form a sacred street located between the Temple of the Sun and the Royal Palace.

Detail of one of the fountains.Photo C. Zeballos


Wright and Valencia suggest that the secret of the citadel's longevity lies in its drainage system. They even state that this is the most important element of the city, even if it is underground, here is where the Incas put around 60% ​​of their efforts.

The researchers propose eight major components in the drainage system:
1. A central main drain, called Dry Moat and that separates the agricultural zone from the urban area.
2. The drainage of the terraces has good longitudinal gradients that lead to the longitudinal drainage.
3. Underground drainage terraces, consisting of pieces of rocks of low quality, with overlapping layers of gravel and sand (see picture).
4. The drainage surface in areas with grass was used to drain water from the sloping roofs and plazas.
5. The drainage channels were combined with ladders, walkways or interior of temples.
6. A deep layer of chunks of rock beneath the plazas allows the runoff from tributary areas.
7. A good system consisting of 129 drain outlets distributed in retaining walls.
8. Strategically underground caves used to discharge sewage.

Typical surface drainage outlets in the walls of Machu Picchu
Image courtesy


In 2001, a team of geologists from the Institute of Disaster Prevention Research at Kyoto University led by Professor Kyoji Sassa, conducted a series of studies determining that the ground beneath the citadel of Machu Picchu is moving. According to the Japanese scientists, who buried instruments on the slopes around the citadel, there are alarming signs that would risk a slide of the mountain, as even some of the pieces of Inca masonry are separating. Click here to see the report in English.

Landslide prone areas the team at Kyoto University. Photo courtesy of H. Shuzui

However, several scientists as Gary R.Ziegler have labeled these studies as alarmists. Ziegler says that while there is movement in the area, is a "gradual collapse" involving several million years. Indeed, comparing the photos of Bingham nearly a century ago, no major change in the structures (except in the area of ​​the hotel). In addition, there are few examples of solid granite mountains Huayna Picchu Machu Picchu have collapsed in the period leading human history. Finally, the area seems out of the zone of earthquakes that shook Cuzco and other areas and away from active volcanoes.

Comparison shows that the separation of the stones in some areas is practically the same after 41 years. Photos courtesy of G. Ziegler.

With some irony, Ziegler concludes, "We respectfully suggest that the magnificent work of engineering at Machu Picchu will remain intact for much longer than Cassandric Japanese team that predicts its imminent destruction. "

For the sake of the ruins, I hope Ziegler is right, however it would be advisable for the relevant authorities to be alert, especially because after having been chosen as one of the 7 New Wonders, Machu Picchu is expected that more will receive lots of tourists.


The archaeological complex of Machu Picchu and Tipon were recently honored by the American Society of Civil Engineers (ASCE) for their "Civil Engineering excellence".




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  4. Its walls, terraces and gigantic ramps give the impression of having been sculpted in the escarpments of the rock, as if they were part of it. The natural frame, located on the eastern slope of the Andes, is part of the upper Amazon basin, which has a very varied flora and fauna.

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