Chaco Culture National Historical Park
Chaco Canyon, New Mexico

The round structures are "kivas," often described as a "church" by present day Pueblo people. They were really more, but did provide a space for religious rituals as well as social gatherings. All these structures had wooden beams and slats set across them for ceilings, with dirt and adobe masonry over the wood. Of course over the years the wood rotted and collapsed the ceilings. What we see today was excavated by archeologists from the National Geographic Society and the Smithsonian in the 1920's and 1930's.