They didn't build that.
the pyramids are electric power generators, based on the same concept as the tesla tower. Built over underground water, creates "free electricity". You can find experiments where people layered granite and limestone(and some basalt sometimes) and discovered it could be organized to create a natural amplifier.
More mysterious is the sphinx, which best guess is thousands of years older than the pyramids depending on who you listen to.
They found "natural" constructed nuke reactors in Africa, basically a sloped underground tunnel with radioactive material in them, and then appropriate strata to allow amplification and collection of the energy. I forget those exactly how they work but info is out there. They are deffinately not natural occurring caverns.
Ancient tech is out there and being kept from us. Many speculate it is in the vatican. That the library of Alexandria that was burned was first pillaged and the knowledge moved to rome, and eventually into the vatican.
Regardless, our own history IMO is much better known and understood than what we are allowed to know, because knowledge is power and knowledge like that could create a monumental shift in society. I have wondered if the people investing in EV's are also in the know about how the pyramids worked and want to see EV pushed because once the pegs are in place they can release the magic pyramid energy and then watch their investments grow exponentially as the electricity conundrum is solved. But that may be too short sighted also.