 There are clues that at least some humanoids were involved in making the monolith. It had a poured concrete base, which was attached to the object with the kinds of nuts and bolts you'd find at the hardware store. It feels like sheet metal almost, a little more dense. Doesn't have as much give, but definitely sheet of metal. And you weren't whisked away to another parallel universe? I don't think so. Maybe there's a special knock that you have to do. I just did the classic one, two, three. I don't know the secret code.