First used on these shores by Native Americans, adobe brick is a mixture of soil, water, and straw that's set in wooden frames and baked by the sun. When adopted by Spanish colonists, the adobe home as we know it sprouted: a low structure with flat roofs (in areas with little rain or snow), thick walls, and few windows, to keep the sun from shining in. Timbers, called vigas, pierce exterior walls, forming the framework for ceilings inside. Fireplaces in the corners of the house warm rooms on cool nights. During the heat of the day, a central courtyard serves as an open-air room for relaxing and socializing.