The ancients mapped the globe, developed our level of technology and then destroyed themselves....we aren't them. They were larger than us and a few survived their wars. They lived longer lives and as such they slowly died out, we came along after they died and were possibly slaves or workers for them.

We evolved and stole tools and fire and various weapons. We then fought a war and one (these were the giants and titans of mythology / Noah arks etc)

We said we descended (perhaps some cross breeding?) But we never have the tools. So we adopted the last few megaliths that were not wholly destroyed and rebuilt our current civilization.

Along the way, legends passed down and over time we built up our cultures and had only trace memories left due to our much shorter life spans.

Another one I like is the possibility that Atlantis is in a crater on a larger planet which is hidden from us (Crater earth) - very Verne quality and it was a great rcabit hole. It's available on YouTube via a search for Crater earth theory.

NASA is taking some stuff...but the question is why some...

• possibly other areas on the planet, possibly manipulation on the level of standards....

Possibly esoteric or occult meanings....