China Mieville's Bas-Lag.
I haven't encountered a single world in recent years that was as interesting, diverse and captivating in it's otherness than China Mieville's Steampunk/Fantasy potpourri that was Bas-Lag. It surprises at every new page with ideas that are always vivid, disturbing and utterly creative and Mieville knows exactly how much he has to show and explain for it to remain mysterious and interesting.
Want a taste?
Bas-Lag features....
Trains eternally stuck in time-bubbles, a swimming metropolis made out of a collection of tied together ships, crab and mosquito people, a nation of undead, probability manipulation, shadow and light golems, self-aware steampunk AI's, tooth and color-bombs, mysterious twisting forces that turn whole countrysides into perversions of reality, tropical beaches consisting of rusty clockwork,a so called "crying king" living in a city of water, magics of all possible varieties, gunfights, airship battles, devious political machinations, city consuming demons, embassies of hell itself and much much more.....
The three books of that series (Perdido Street Station, The Scar and Iron Council) are well worth their read, too, since they are not only hugely creative but also feature an always interesting narrative laced with socio-political commentary. Now, go and read them! ^^
Other universes worth mentioning that mostly score through their size and attention to detail than through flashy ideas: The AD&D universe (size wins, also features extremely interesting parts in Planescape for instance), Discworld (It's satire so it tends to just overtly subvert what we already know than invent something entirely new, but oh my god is it good and surprises with creativeness in it's comicalness with each new entry), Tolkien's universe (nuff said), A Song of Ice and Fire (not particularly creative by being strange but by carefully fusing harsh historical realism with carefully inserted mythology and fantasy)