Matterhorn from Zermatt...Taj Mahal...Maroon Bells from Maroon Lake...St Basil's Cathedral....Everest from Kala Pattar...Paine Towers....Half Dome...Grand Canyon...Mt Fuji ...Piazza San Marco and Ponte Rialto...Kilimanjaro from any western angle...Bodie...Kolmanskop...Doodvlei...Big Ben...
The trouble with these spots and similar is not that they are unphotogenic--quite the opposite. The problem is that most of the easy angles have already been shot, thousands if not millions of times. Asking Tom Tourist with his cellphone to come up with something strikingly original when casually visiting is quite a tall order (and Tom Tourist probably doesn't care anyway; he is merely interested in a record proving that "here I am grinning in front of [insert landmark here]".)
For the more earnest photographer, a good challenge would be to visit a series of such spots and see if one actually could produce anything new and interesting. I once tried a night color infrared startrail shot at Maroon Lake; the image has issues including poor sharpness, but one could not deny that it was different.
I remember my parents visiting Rome on a holiday in the early 1970's for their 25th wedding anniversary.
They brought back two packs ( I think there were 30 or 40 in each pack) of view slides of Rome and the Vatican City. I remember watching the slide show and the shots were of all the important views but professionally taken and not the usual ones with a finger in part of the shot or the back or someone's head.
I remember those bought slides well! You could buy them even in places that did not allow photography, like some museums. Most of them were 35mm, but a substantial number were shot on 127 film. Alas, most were shot on cheap duplicating film that faded quickly and the examples I still have are in very poor condition.