This map is the majority of my creative mode efforts all in one map (with a few extras added by friends of mine, usually the bits that look out of place). Just explore it, you'll be surprised what you might find. Even I don't remember most of the labyrinth under the city.
Oh, and if you find a glitched fireball in mid-air deep in a snow biome to the south-west of Cerol, get the hell away from it's render distance before you save and exit. It may or may not permanently crash the world.
But the rest of it's all good :D