USA. Heart Butte, Montana. 1998. Tipi. The tipi is widely regarded as one of the engineering wonders of the world. A portable home, it can be taken down or put up in 15 minutes. In the past, tipi poles were dragged by dogs and later horses. Always facing east, its elliptical shape can withstand winds approaching the force of a hurricane. A fire is made in the center, the top flap used as a flue.