The architecture of Machu Picchu showcases the ingenuity of the Incans; the terraces were built not only for agricultural purposes, but also as erosion control. The terraces shored up the sides of the mountain to fight soil erosion and landslides
The Incans devised an ingenious drainage system
to fight erosion, as evidenced by the numerous drain holes found on the mountainsides. Incans dug out several feet of dirt on the site, then filled the ground with large stones on the bottom, then progressively smaller stones on top, and finally topsoil that allowed water from heavy rains to filter down through the soil, through the rock beds, and flow harmlessly down the side of the mountain.
The stones at Machu Picchu are fit together perfectly without the use of mortar, a spectacular feat for 14th century Incan manpower; all stones were transported manually, some weighing more than 2 tons, and shaped with stone hammers to be a perfect match for the neighboring stone.