To level the sloping alcove floor, the Anasazi filled in behind retaining walls. The altered floor supported rooms and also provided working space and a safe play area for children. Oak Tree House appears to use every inch of alcove space. Some apartments rose four stories to the roof of the inner alcove, and additional storage rooms stood along an upper ledge. Oak Tree House contains about 50 rooms and 6 kivas. Smoke-blackened rear walls show evidence of many cooking fires and the struggle to survive winter.