The credibility of the "Ancient Mysteries" site is immediately suspect, as they include Noah's flood as if it were some sort of reality. However that does not negate the incredible mastery of building technology of the ancients.
mjesse sums it up pretty well - not only were they built without regard to cost and over lifetimes, but with slave labor where the slaves were dispensable. There really was not a whole lot of technology increase between these ancients and civilizations as recent as a few hundred years or so ago. Its not like Chartres cathedral was built using computer guided water jets. The rise and fall of past civilizations produced dynasties of master builders who, over multiple generations, were able to dedicate their every being into creating these wonders. It is civilization itself that enables this, with the ability of certain classes being able to concentrate on great works since the means of survival is take care of by others. Look at the complete failure of civilization in Europe after the fall of the Roman Empire. Plumbing and central heating was established by the 1st or 2nd century, not to be seen again until about 1200 years later. The Romans did not employ "magic", they simply were able to develop classes of engineers since they had plenty of subjugated peoples to feed them.
