A set of sunken terraces starts south of Ollantaytambo's Plaza de Armas, stretching all the way to the Urubamba River. They are about 700 m long, 60 m wide, and up to 15 m below the level of surrounding terraces; due to their shape, they are called "Callejón", the Spanish word for alley. Land inside Callejón is protected from the wind by lateral walls which also absorb solar radiation during the day and release it during the night; this creates a microclimate zone 2 to 3 °C warmer than the ground above it. These conditions allowed the Incas to grow species of plants native to lower altitudes that otherwise could not have flourished at this site.