Because a lot of these structures are very old and some are even under water, I think that they likely existed during the ice-age. Later cultures like the Incas build on top of these huge structures.
Paper via wikipedia: https://www.tandfonline.com/doi/abs/10.5408/0022-1368-40.1.2...
> It is not easy to give a geological education to a brilliant and determined chemist.
Savage
... "Several people tried to discover the secret of this stone making. They were successful in softening the limestone that they reduced to a soft mass. But they failed to harden it again. This has been the reason, why, 40 years ago, Davidovits and Aliaga stopped their studies. They could disaggregate (limestone) but they were not capable to re-agglomerate it, to harden it again.
The appropriate knowledge was acquired very recently (2 years ago)"