In early times, the Navajo lived in small family groups rather than in villages. They lived in hogans – dark, gloomy structures made of tree bark and mud. The door of the hogan always faced east toward the rising sun, and had a small hole at the top of the dome to allow smoke to escape. Most Navajo families maintained a hogan in the desert and a hogan in the mountains so they could move quickly if the weather turned, the water supply dried up, or new grazing land was needed.