TheBoost said:

Darth Hade said:

To tell the truth, I never liked the look of "the cave" in ESB. I didn't like that it looked like some sort of hidden or long buried structure. It should have just been a cave, nothing more.

While I've never wanted the explanation, I've always liked that there was a structure there. It hinted at something ancient and mysterious. Implied a richer backstory than we'd ever get to know.

This.

"a domain of evil it is." That's all we really know about it. I've always figured that it's like an ancient Sith temple or something.