Inca architecture
The Incas also developed an extensive road system spanning most of the western length of the continent and placed their distinctive architecture along the way, thereby visually asserting their imperial rule along the frontier.
[3] The most common shape in Inca architecture was the rectangular building without any internal walls and roofed with wooden beams and thatch, usually made from ichu.
Inca architecture is widely known for its fine masonry, which features precisely cut and shaped stones closely fitted without mortar ("dry").
[20] They argue that according to ethnohistorical accounts the Incas were impressed by these monuments and employed large numbers of stoneworkers from nearby regions in the construction of their own buildings.
[21] In addition to these references, they also identified some formal similarities between Tiwanaku and Inca architecture including the use of cut and polished stone blocks, as well as of double jambs.
According to Ann Kendall, the Huari introduced their tradition of building rectangular enclosures in the Cusco region, which formed a model for the development of the Inca kancha.
[24] There is evidence that such traditions were preserved in the Cusco region after the decline of the Wari as is attested by the enclosures found at sites such as Choquequirao (Chuqi K'iraw), 28 kilometers southeast of the Inca capital.
Hyslop comments that the 'secret' to the production of fine Inca masonry “…was the social organization necessary to maintain the great numbers of people creating such energy-consuming monuments.” Spanish Chronicler Pedro Cieza De Leon wrote that Pachacuti "ordered 20,000 men sent in from the provinces" for the construction of Sacsayhuamán.
Additional surface smoothing near the edges of blocks has been attributed by some researchers to a chemical etching "mortar" composed of pyrite mining slurry and plants containing calcium oxalate.
[31] Some species of bacteria from the genus Thiobacillus are able to process sulfidic minerals and produce sulfuric acid as a byproduct; complexation with oxalate increases the etching potential of the mixture.
This, in combination with masonry thoroughness, led Incan buildings to have a peerless seismic resistance[31] thanks to high static and dynamic steadiness, absence of resonant frequencies, and stress concentration points.
Ashlar masonry was used in the most sacred, elite Incan structures; for example, the Acllawasi ("House of the Chosen Woman"), the Coricancha ("Golden Enclosure") in Cuzco, and the Sun Temple at Machu Picchu.
[35] In particular, Inca walls practiced mortarless masonry and used partially worked, irregularly shaped rocks to complement the organic qualities and diversity of the natural environment.
[37] Inca employment and integration of the natural environment into their architecture played an essential role in their program of civilizational expansion and cultural imperialism.
[35] For example, in the royal estate of Chinchero, the Incas adapted their large-scale earthwork and massive stone construction to the land's dramatically steep valley in order to create intense, visual drama.
