The Pueblo people lived in the Southwestern United States in communities called pueblos. They built houses out of adobe, which is mud and straw that is dried into strong bricks. The bricks were stacked to form walls, with gaps filled with mud. Wooden posts inside supported roofs covered with layers of sticks, grass, mud and plaster. Some pueblos contained over 100 rooms and large underground ceremonial chambers called kivas. Adobe houses could only be built in very dry areas due to the material dissolving in rain.