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Many innovations were taken from previous civilizations namely the Moche, Tiwanaku, and Chimu. The Inca Empire was able to flourish through these innovations that they implemented while inventing some of their own. The Inca constructed terraces and buildings in Machu Piccu, which are fitted together so well, without the use of mortar, that you cannot fit a knife blade between the stones (Cock 20). The stable construction was needed in the volcanic-active Andes and has lasted until the present time. Near Cuzco and at Machu Picchu they created level surfaces for irrigation and grow mostly corn and potato crops while reducing frost risks by breaking the down slope flow of cold air which also allowed for irrigation canals to flow across the slopes (Marston, Knox, Liverman 16). Constructing the terraces required considerable technical expertise and social organization, the Inca rulers requested large numbers of laborers from each local community. Many terraces were abandoned because the native labor force was reduced to the ravages of newly introduced European diseases and the need to shift laborers to the Spanish mines in the sixteenth century. But, for over 500 years the massive retaining wall and staircase terraces have kept Machu Picchu from washing off the cliffside. The Inca's possessed only wooden, stone, and bronze tools consisting of axes, clubs, maces, slings, and spears and relied on their own labor to move the heavy blocks. Those that lived in the desert would divert mountain runoff into aqueducts, built underground to limit evaporation, which carried water to irrigation canals. The Incas were the people in all the Americas who had the highest level of animal-keeping and cultivation. In all, their advanced terrace cultivations handled forty different crops cultivated with effective tools of agriculture, like the taclla foot plow. Fertilizers were used; guana - excrements from bats and birds, and the irrigation technology was well developed (Mangudai 1).