@Astronomer_Mark I think the Grand Mosque in Mecca is the answer but if it's too big to count as an "object" then the Kaaba, at its centre. Thousands of years old and seen by millions of new eyes every year.
@Astronomer_Mark It's a great question and I'd love it to be the ISS but I don't think it's likely.
I think we need to look at an object in the modern era and in a big city for a high turnover of people. The clock tower in Mecca or the Statue of Liberty spring to mind.