something fun i came across on wikipedia this morning:

plans were floated in the 1960s to demolish a large chunk of Midtown Manhattan in order to build a super expressway directly across the middle of the island. ideas included that the freeway was to sit ten stories above the ground, and that new skyscrapers would be built on top of it and other buildings below it. in probably the biggest wtf moment, there was also a brief flirtation with the idea that it would actually go right through the Empire State Building, occupying the building's 10th and 11th floors.

http://en.wikipedia.org/wiki/Mid-Manhattan_Expressway

strangely the idea wasn't popular with the local residential or business communities and died a death.