It's really a strange level design decision... it doesn't look good. It's like something put in to test the engine, but was left there mysteriously. I can't find any discussions about this weird "spike" on the net either.

But I know for sure, that if I would create an epic easter egg, I'd make some kind of puzzle around something you barely notice -- yet something where your subconscious feels that it's strange, yet your conscious mind thinks nothing of it. The spike is a perfect example of that.