Mesa Verde National Park contains about 600 alcove sites, about 90 percent of them with fewer than 11 rooms, and at least one-third are single-room structures that were probably storage rooms for a nearby cliff dwelling. Only about a dozen cliff dwellings contain 40 or more rooms, including Oak Tree House, one of the larger cliff dwellings on Mesa Verde. Its residents lived in a busy neighborhood, with Fire Temple and New Fire House just up canyon, Sun Temple above on the canyon rim, and many other cliff dwellings nearby. At least one spring flowed from nearby cliff walls to supply fresh water. Refuse such as animal bones and broken pottery was often tossed below into middens. Plazas, made in part from kiva roofs now missing, provided well-lit open spaces for many daily activities. Sloping alcove floors were leveled by filling behind retaining walls, which supported walls and created work space, and additional storage was placed on ledges within or near the dwelling, reached in part by rooftops of lower story buildings. Oak Tree House contains at least 60 rooms, with well-built stone masonry walls supporting multiple stories, and the alcove itself sometimes serving as a roof for upper rooms. Doorways were rectangular or T-shaped, though the purpose of the T-shape remains uncertain and may have been symbolic, eased entry into outer rooms, or signified public use rooms. Oak Tree House has six kivas, each surrounded by adjacent rooms, and each kiva with its set of rooms may have been used by an extended family. The sequence of life in the region moved from semi-nomadic people and pithouses in 550 CE to single-story villages by 750 CE, multi-story villages by 1100 CE, cliff dwellings and late mesa top villages by 1200 CE, and migration by 1300 CE.