Question

Where on earth would you have to stand for the sun to pass directly overhead (i.e., pass through your zenith) at some time during the year?

Answer 1

In the tropics where the Earth you have stood for the Sun to pass directly overhead that is passing through your Zenith at some time of the year. This id is also known to people as within +/- 23 degrees to the equator. Hence, the answer to the question is "on the topic or within +/- 23 degrees to the equator".