Skynet said:
Or maybe it is related to an unfinished location called "Abbey".
A medieval, spooky castle as a post-apocalyptic and American wasteland location? Nah, I don't think this was in any way meant for the Abby. Besides that, how do you think it was going to be used in the engine in any case?
I'd go with Silencer's suggestion that it's a leftover from an early build of the engine when they may have thought of using it for a medieval RPG, since that tech demo was just a demonstration and exploration of a hex-based isometric engine.