That's the premise of Crawler Town, an entire town mounted in a gigantic platform that looks pretty much like an enormous version of NASA's crawler or the Jawa Sancrawler, which is pretty much the same thing but for tiny people.
Flickr user Dave DeGobbi not only prepped for the Lego Apocalypse (Legopocalypse? Armalegon?), he survived it in style. He explains his post-apocalyptic creation:
Crawler town roams the barren wastes of a post steam-punk world after cataclysmic climate change do [sic] to excessive coal use. Several such cities exist but Crawler town is the most popular due to the Aero 500 hydrogen fuel cell Air races that are held. Many people travel the wastes to Crawler town for vacation and to enjoy rare luxuries like Pizza, fresh vegetables and Beer. Travelling the wastes in search of minerals and aquifers ( vital for survival) the mobility of the city keeps it away from the vicious sand storms of the wastes.
I have no idea what an "Areo 500 hydrogen fuel cell" is but the rest of the city-on-wheels sounds pretty luxurious considering the circumstances.
It's a detailed creation, too, with "functional powered treads for movement , full suspension and front and rear steering. [It includes a] working crane, hanger slides for planes and lift from upper and lowers levels."
Here's a taste of the behemoth. Hit DeGobbi's Flickr after the jump for more pics.