I've searched around and it seems like most people are using tile-based map systems.
I suppose this question is more theoretical than practical (I am not very concerned about memory or performance speed), but I want to know: what other ways can a map be created in a game?
A map being a graphic representation of terrain that can be navigated, has entrances and exits, and boundares (no-go zones).
Besides using text files to store and arrays to load tile data, one idea I had was to store a map entirely as a graphic file and use queries on the pixel colour to determine boundaries (ie, you can only move in a certain direction if the way is bright enough in that direction).
What other creative map systems are out there?