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 mountain. However, it has been found that the terrace farming area makes up only about 12 acres of land, and a study of the soil around the terraces showed that what was grown there was mostly corn and potatoes, which was not enough to support the 750+ people living at Machu Picchu. Therefore, when studies were done on the food that the Incas ate at Machu Picchu, it was found that much of what they ate was imported to the area from the surrounding valleys and farther. Although it was located only about from the Inca capital in Cusco, the