Although I've stopped playing it, the development of the vast, ponderous, procedurally generated, obsessive-compulsive amazingness that is the Dwarf Fortress computer game continues to fascinate me. The two programmers have set forth a task truly worthy of a Demiurge: to represent everything in a vast and random fantasy world, down to the last severed left toenail of a naked mole rat, down to the last one-humped camel leather loincloth and prickle berry bush. What it lacks in graphics (strictly ASCII), DF makes up for in detail.
random city maps just cries out for Photoshopping into a campaign. Draw on a wall, some big buildings, street names and you're good to go!