I believe that most of the megalithic building sites employed water used as ballast. This goes twice over at those sites where great amounts of material were lifted to great height. It's improbable many of these employed cold water geysers because these events are relatively rare. But in most cases they had presasurized water by some mechanism. Even today at Machu Pichu there is a stream that originates near the top of the mountain. Evidence suggests the flow was much greater in the past. Central American pyramids are always associated with cenotes. I really haven't studied any other sites or situations but even the Sumerian writing refer constantly to water coming out of the ground.

Do I know of anyone confirmed to have used CO2 geysers? No, of course not. Though if you compare what we know to what exists you'll find that little of it is really explicable in terms of what we know, or what we believe they knew or were capable of. We don't really have a clue and that might be because we've been barking up the wrong trees. We might really misunderstand all the ancient people and it might even be related to something so incredible as the story of the Tower of Babel. Perhaps it was more than the language that became confused. The story itself is written in the old style so we misapprehend it as well.

I refuse to discount the ancients especially when their words even cross civilizations. It is our duty to prove them crazy if they were. It is not fair to simply dismiss it all as the ravings of lunatics. Asking me for proof is about as productive and meaningful as seeking the ancient writings of a child or a scientific treatise on the flow rates of artesian wells relative to top pressure. This is a very simple thing to prove or disprove but if it could be proven from where I sit it would long ago have become accepted fact.

I would remind you that there is simply no compelling reason to attempt to harness such energy today. But before the invention of internal combustion engines and electric motors the only energy available was from harnessable natural processes. Falling water would certainly attract people even before anyone thought of using its weight to do work.

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Man fears the pyramid, time fears man.