Reddit mentions of DK First Atlas: A First Reference Guide to the Countries of the World (DK First Reference)

We are not "dead." When someone posts, it might take a day or so to get a few replies, but we get relevant posts and replies pretty darn often for having shy of a thousand subscribers. We have many valued contributors which I have awarded flair so everyone knows who they are (and if anyone ever sees anything super-awesome, just send me a message pointing it out, and I will either put it in the sidebar or award them "active member" flair).

Also: Moms are certainly welcome here, and I like to think that we will have more resources and knowledge about developmentally appropriate activities than the average parent (and that's not to say that parents can't know, just that usually they are going by their own experiences (not based in science) and are biased towards their own ideology).

Anyways, It sounds like you have a really curious three-year-old and in addition to the other good suggestions, I have some ideas.

My First Atlas is a really good book for any child ready for the information, which it sounds like you little one is, already.

There's also a really cool demonstration you can do with him to demonstrate axial tilt.

You could also take him out to some different local landscapes and build them with him using paper mache, and help him name the land-forms. . .

And I also have to say that this is really mature subject matter for a three-year-old. It's a big concept. I personally never let that stop me from trying to explain things (with lots of analogies, visuals, and hands-on activities). He might not get everything exactly but that's OK. Later when he hears the information, he'll have a foundation on which to build it on. :)

Hope this helps, too. And if I think of more, I'll come back and edit.