Dry stone from the arable or cultural land. They serve both as cattle/sheep fences and the lot's borders. Sometimes also the dry stone terracing is apparent, often combined with parts of stone masonry (house foundations and shed walls) that are held together by a clay-cum-needles "composite" mortar. In Peru in the 15th century AD, the Inca made use of otherwise unusable slopes by building dry stone walls to create terraces. They also employed this mode of construction for freestanding walls. Their ashlar type construction in Machu Picchu uses the classic Inca architectural style of polished dry-stone walls of regular shape. The Incas
Machu Picchu were not perfect, as studies of the land show that there were landslides that happened during the construction of Machu Picchu. It can still be seen where the terraces were shifted by landslides and then stabilized by the Inca as they continued to build around the area. It is estimated that the area around the site has received more than 72 inches of rain per year since A.D. 1450, which was more than needed to support crop growth there. Because of the large amount of rainfall at Machu Picchu, it was found that irrigation was not needed for the terraces.