The goddamn world !! Or at least a "bigger" part of it, like Europe.
It would be awesome to travel from here to there on a huge map.
Just imagine, if you want to go to another country you'll have to go to the airport (which would be realisticly populated), buy a ticket and stuff, and enter the plane.
Of course the flight itself would be skipped, but all the stuff around would be awesome. What if you wan't to smuggle drugs? Hide them in your bag with the risk of being catched by the security or police.
I got the idea from "Blow", just to mention