A few years ago I created two reference images to illustrate how large the Tablelands of the Dark Sun setting really are. And they were wrong. There’s different maps of Athas that show different scales, and the one that I used back then more than doubled the real distances between any two places.
These two images are based on the hex travel map from the original first Dark Sun box, which agree with the statement in one of the books that the journey from Tyr to Urik is 170 miles (if you follow the road).
As you can see, the entire region is about the size of Colorado, Utah, and Wyoming, though that includes many of the truly barren wastelands surrounding the inhabited areas.