Going to Places & Not Seeing the Sites

On Twitter this evening, I had a tweet conversation with Lavie Tidhar, who was stuck in the Athens airport with no time or ability even to do a crash few hours of sightseeing. But, he pointed out, he'd been in China and never seen the Great Wall, and in Paris and never gotten close to the Eiffel Tower.

What well known place have you been and missed its most (or a most) famous landmark?