Maps That Never Happened

I can add these ones.

A plan for a motorway round the centre of Edinburgh:

http://www.gcat.org.uk/blog/?tag=edinburgh-motorways

Churchill's Operation Unthinkable for an attack on the Soviet armies in Eastern Europe by Western forces in the aftermath of WW2:

http://en.wikipedia.org/wiki/Operation_Unthinkable

On a smaller scale in the town next mine lies a very large roundabout that I took as an urban design wart. Recently I accidentally learned [1] that it was built to fill the hole left for a national road exchanger. The national road project never completed due to public resistance.

[1] partially thanks to wikipedia