Pangur Bán
Deconstructed
That can't be correct at all. For starters even the Eiffel tower is probably visited more. Then there are other stuff like the Acropolis.
I have once modelled the Notre Dame. It has historic value, yet the actual spire is less than impressive. It isn't on a monumental scale either - you can fit the entire thing inside the Hagia Sophia, using mostly the space below the central dome.
They said it was on the BBC, and I googled it and found that the Grand Bazaar tops it. I'm sure there are multiple ways of calculating this or deciding who is a tourist. BUT ND is a church and is free (except for certain areas), whereas I think Eiffel Tower is ticketed and expensive. I've been to ND and not ET, so maybe I'm a case in point.