All true.
But just because it's been made into an "art project" (apt description, imho) doesn't mean that it didn't actually exist, albeit in a somewhat more reasonable form than the art project version.
If reasonable means without the spaceships, Uber-people and healing energy crystals then i agree, in theory.
Although the real place might hardly be recognizable as the myth version.
If you know about the small jungle village which, most likely, inspired El Dorado myth, you know what i am talking about.