Yes, it's another waterfall. It's like someone was experimenting in Iceland: "Hmm, let's try a blue water waterfall. Let's try a black stone waterfall. I know! Blue water AND black stone!" (Given his proclivity for the Norwegian fjords, I suspect Slartibartfast from Hitchhiker's Guide to the Galaxy.) In any case, this waterfall, Barnafos, was another beautiful variation on what you can do with rushing water and a little gravity.
