i found that world too, i dont sure it 1000X1000 but
it too big to be 400X200 or 200X400 or 300X300..
how we can get that big world ?!
pleaes answer
In the past it used to be possible for more savvy users to edit the parameters of their worlds by hacking, this has since been fixed and only a few of these worlds remain. I know Atilla has a couple and Lrussel has one, there are probably a couple more though. You can't fill the world and save it though, since there isn't enough space to save any more blocks than can fit in a great or huge world at the moment.