Oblivion Remastered, you've probably noticed that Tamriel's other regions are all shown on the map. Bordering Cyrodiil are Hammerfell, Elsewyr, Valenwood, Morrowind, Black Marsh, and Skyrim, and it turns out you can actually travel to a lot of them.

For those that don’t know, The Elder Scrolls: IV Oblivion is set in Cyrodiil, which borders Skyrim, the setting of The Elder Scrolls V: Skyrim. Hence why you can see The Throat of the World at the edge of the Oblivion Remastered map, assuming you can climb high enough.