The oldest forms of indigenous shelter were often round in shape. (Think the Southwest USAHogan,Mongolian Yurt, North American Teepee and the Greek Tenemos, among others.) Why did our ancestors choose to build round? Because the ovid shape — eggs, earth, tree trunks, and stones — is what they saw reflected in the surrounding natural environment. And, as usual, Mother Nature knows best. There is some nifty natural science that makes round buildingsmore comfortable, more energy-efficient and safer — especially if you combine the ancient shape with modern materials!