oh well, do you see the plausibility of these structures
being roasting/smelting furnaces?
My first thought was a sink with a drain but I can't imagine why someone would go to all that trouble to make a sink.
My second consideration was that someone could attach bellows to a pipe leading to that center hole and use it to force air into a fire thereby making it hot enough to smelt iron, so, yeah, with that caveat I can see it as a possibility.
I am reasonably positive that it is NOT a Bosnian pyramid.