Speaking of the Great Pyramid, the bulk of it is crudely cut, but the outer casing and the lining of the interior chambers has gaps well below 1 mm in width. These stones are about 2.5m long, much longer than a typical human, and weigh several tons. Not only had they to be cut to sub-millimeter precision, they also had to be installed equally precisely. This takes serious engineering chops, especially when you don't even have steel.