I noticed it while at FT Dawnguard. I went to my quest log and chose map, the entirety of Skyrim was clear. You could even see some of the provinces like High Rock, Hammerfell, Cyrodill, and Morrowind. Granted it's all dark, but no clouds are on.

It also works just by going onto your map while in FT Dawnguard. So far, not other place works.

The entire continent of Tamriel is actually crafted in the game.