Hi Zach;

That's a really great question. And I'll first give the typical scientist response, "I don't know!" :-) But seriously, there are a couple of ways to answer that question. First, what you see at the surface really is 3-D, and the penumbra (the outside filamentary part of sunspots) is a bit 'higher' than the umbra (the dark centers). When you look at a sunspot as it's near the solar limb, you can kinda see in this image below. The difference is a few hundred kilometers. The second answer is that we really don't know what sunspots look like underneath the surface. There is some indications from how sunspots behave that they have a connection (or a good memory!) to where they came from deep in the solar interior -- that could be hundreds of Megameters (a Megameter is 10^6 meters, or a thousand kilometers) We can also try and study their structure using helioseismology (and the Google page on that is pretty good, and written primarily by a colleague here at my institute), using essentially sound waves to probe beneath the surface....but, it turns out that the helioseismology signals that we want to use to look beneath the surface and see how deep sunspots go are, themselves, kinda messed up by the presence of, guess what, a sunspot. So it's never easy. But we're working on it. If you have any ideas, let us know?