Is it that the wonders we have today are so much easier to achieve than those in the past? A building bigger than the pyramids can be constructed now in less than a year whereas the pyramids themselves took years to build.

Or perhaps our wonders are no longer macroscopic but microscopic - advances in science and technology which may not dominate a skyline but do make big changes in the world.

Now, a true wonder I would like to see which may rival the pyramids is a space elavator... If you don't know what one of them is, its a satellite in geosync orbit with a cable descended down which can pull up elavator cabins (pressurised, of course). The cable has to be carbon nanofibre which we haven't (yet) got that is light and strong enough to do the job and the thing itself would be extortionately expensive to build (which is the other reason we don't have them at the moment) but once one is made it becomes a cheap (almost energy neutral - no wasted fuel) way to get into space.

Apparently it is possible to do this and this would indeed be a wonder. The reason we have not built one - the money. Big projects need someone with a massive ego and a bottomless purse and enough slaves (well, salaried employees) to get the job done and a single minded focus on that goal with a will to complete it regardless of the cost. Autonomic monarchs like the pharohs had all that, dictators like Napoleon and Hitler had it (to a lesser extent). Modern bureaucratic governments with committees querying every expense certainly do not have it. The closest we have are eccentric Billionaires like Richard Branson and he spends all his money on epic balloon trips.