The X-Seed 4000 is a proposed structure which would be as high as a mountain (4km/2.5mi) and would be able to accommodate up to 1 million inhabitants. It was created by architect Peter Neville in 1995 in a bizarre, but effective publicity stunt for an architecture firm. The plans for this astounding building were actually completed. It would need at least 3 million tons of steel and the hefty sum of 1,000 billion dollars to build. According to Neville, the structure would have been built in Japan.
We are not responsible for the contents of external links. Full disclaimer can be found here.
By Newsburst (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons