First humans lived in caves because they had no technology to build better houses. Yet, the caves had a great advantage: they were free!
Today, we have great houses but they don't come for free. So, a 24-year-old Chinese architect who wanted to live rent-free decided to go back to a cave. He built himself a mobile egg-shaped house. The six-foot-tall, solar-powered, egg-shaped abode is made of bamboo, wood and grass seed, and fits easily on a sidewalk. (see the picture).