Imagine a building that spanned the U.S.A horizontally

http://io9.com/5867782/too-bad-this-one+million+person-city-from-new-york-to-san-francisco-was-never-built?popular=true

http://www.butchersmarket.com.br/indexhibit/indexhibitv070e/index.php?/ill/mega-structures/

It was proposed by Alan Boutwell and Mike Mitchell in 1969. It would have been well underway if not long finished.