I cant believe London, New York or Las Vegas make it on to this list, probably my 3 favourite cities in that order.
For me it's the Pyramids. You imagine trecking through the desert to find three solitary pyramids standing majestically above the Sahara. What you actually get is the Egyptian equivalent of the M1 steaming past full of burger kings and KFC's, whilst Arabs try and sell you tacky souvenirs to remind you of the experience.
One you get inside you see that tourists have decided that the only thing missing from this wonder of architecture that's stood for thousands of years, is to let you know that "Deano was ere 1986"