With a one mile wide base and a staggering two mile high rooftop, the Ultima Tower by Eugene Tsui is inspired by nature: the elegant termite mound. It is aerodynamically efficient, resistant to earthquake shock waves, and is cooled by flowing water.
OK, so let's put aside the fact that if the Earth ever reaches the point where we need to house over a million people in one building, we will have bigger problems than putting a roof over our heads. Let's just roll with this one because the design is really cool.
Know what's just as cool as this buildings size? It's price, at $150 billion!