[grimman]

Ultimately there are very simple explanations for most things. You'll have developer/mapper playgrounds where they model new stuff and try things out before cutting them or implementing them. Sometimes these things happen in production maps, and are simply overlooked when they are no longer interesting. It's cruft, but for explorers they are so much more.

Other times they are really nicely fleshed out, but locked away behind flimsy "gates", and really were intended to go into the full game, but had to be abandoned at the very last minute.

And then there's the cinematic areas that are made for show, implemented as they were intended, which never included being accessible to players.

What's really the most rewarding thing about this is that you, as a player, as an explorer, get to puzzle things out; you almost get to write the narrative yourself.