I think it just goes to show that we still know very very little about the Earth's history and the history of our own civilizations.

Much of history is purely interpretation and speculation examining these old places based off what still exists and trying to guess what happened.

What we never get to see are things that no longer exist so it heavily skews our perceptions and we're just left with duct taping fragments of facts to create theories.

It's really fascinating! The world's such a big and ancient place. Tons of mysteries out there. Ancient groups all over the world made such megalithic things and no one seems to know how they did it. Personally I think the technology they had access to was way more than simple hand tools and not many historians consider that possibility. And there may be other civilizations we don't know once existed.