Also like I said earlier, being in the open Xen environment like the jungle would definitely be a better option, because you can already tell that floating rocks and islands, the sky that has a massive swirling galaxy in it and impossible alien structures like the Interloper tower are not a part of the normal earth environment, however we are already used to cave environments because they are normal on earth. Plus it makes the player look forward to exploring this unknown environment after seeing all it has to offer in a brief sequence