I just came across a video by Jesse Cox of OMFGCata and he apparently had some 40 other people get together on this one Minecraft server, that... seems to be heavily modded and it seems to be Zeal/blood elf- inspired floating city that is built on top, within, and below the floating terrain. The end result is epic!
http://www.youtube.com/watch?v=jAjd1vfbiHQ
