The valleys of the Urubamba and Patakancha Rivers along Ollantaytambo are covered by an extensive set of agricultural terraces or andenes which start at the bottom of the valleys and climb up the surrounding hills. The andenes permitted farming on otherwise unusable terrain; they also allowed the Incas to take advantage of the different ecological zones created by variations in altitude. Terraces at Ollantaytambo were built to a higher standard than common Inca agricultural terraces; for instance, they have higher walls made of cut stones instead of rough fieldstones. This type of high-prestige terracing is also found in other Inca royal estates such as Chinchero, Pisaq, and Yucay.