Hmm... Where could this be? The door-thing looks like a computer chip. And the walls sorta look like circuit diagrams?

So possibly inside a large computer? ... Well, it's a dreamworld, why not? ... Although, I forget if we've seen hints of any technological enemies anywhere, either in the music or any other art.

... Perhaps this is what the inside of the crystals are like?

I'm the 43th view, and the first commenter? Huh.