This is a common way to ask a question that is purely imaginary. People ask questions like this to find out about a person's interests and personality in a playful way.

Here are several other similar questions:

If you could be any animal, which one would you be?

If you could visit any country in the world, which one would you visit?

If you could have dinner with anyone throughout history, who would it be?

When you answer these questions, your answer should start with "I would...":

A: If you could live in any period in history, which one would it be?

B: I think I would live in the Old West.

Questions like this are called "hypothetical questions".