I don't think I've ever seen as unique a Lego creation as this "eco punk" mobile town, created by Dave DeGobbi. As it should, Crawler Town has its own little backstory:
Crawler town roams the barren wastes of a post steam-punk world after cataclysmic climate change do 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.