Cliff Palace at Mesa Verde National Park is the largest cliff dwelling in North America. There are over 600 cliff dwellings at Mesa Verde, though only a few are open to the public & we visited three of those... From Wikipedia: "Tree ring dating indicates that construction and refurbishing of Cliff Palace was continuous from c. 1190 CE through c. 1260 CE, although the major portion of the building was done within a twenty-year time span. The Ancestral Pueblo that constructed this cliff dwelling and the others like it at Mesa Verde were driven to these defensible positions by increasing competition amidst changing climatic conditions. Cliff Palace was abandoned by 1300, and while debate remains as to the causes of this, some believe a series of megadroughts interrupting food production systems is the main cause. Cliff Palace was first discovered in 1888 by Richard Wetherhill and Charlie Mason while out looking for stray cattle. The Cliff Palace was constructed primarily out of sandstone, mortar and wooden beams. The sandstone was shaped using harder stones, and a mortar of soil, water and ash was used to hold everything together. "Chinking" stones were placed within the mortar to fill gaps and provide stability. Many of the walls were decorated with colored earthen plasters, which were the first to erode over time. Many visitors wonder about the relatively small size of the doorways at Cliff Palace; the explanation being that at the time the average man was under 5' 6", while the average woman was closer to 5'. The Cliff Palace contains 23 kivas (round sunken rooms of ceremonial importance), and 150 rooms and had a population of approximately 100 people. One kiva, in the center of the ruin, is at a point where the entire structure is partitioned by a series of walls with no doorways or other access portals. The walls of this kiva were plastered with one color on one side and a different color on the opposing side. It is estimated that around 100 people inhabited Cliff Palace during its time of use. It is thought that Cliff Palace was a social, administrative site with high ceremonial usage."