Would we have technology to construct cylinders 2100 feet deep today?
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Likely not, but then we do not have the tech to build the Pyramid complex at Giza [ which is much more than piles of stones ]; nor ability to carve granite stone bowls like those made during pre-dyanastic times in Egypt; nor lifting and carrying 200-500 ton blocks found in other monuments around the world.
lost worlds for sure, very strange purposes to all the things