Wow, look at these guys, saying about the whole "did you think you could carry on." Let me spell it out for you, babies.
I THOUGHT THERE MIGHT BE SOMETHING MORE IMMERSIVE AND INTERESTING THAN AN UNREALISTIC INVISIBLE WALL.
Herp a derp derp, people, seriously.
Like what? I'm sure bethesda discussed this very topic for hours so if you have a better idea they'd probably like to hear it and so would I.
Skyrim isn't floating in mid air. Mountains are useless due to the free roam nature of the game, they don't actually provide much in the way of blocking the player since you can travel over all of them.
You can't just have some over powered creature come in and kill the player because that would be stupid and not fun.
Skyrim is part of a world geography so you can't just have repeating land textures for infinity otherwise it wouldn't make sense. If you know the geography of tamriel then it would be strange that You are clearly far into cyrodill yet...there is nothing there?
This is literally the only way to do it. A little text message is the most immersful way out of all of them. A creature would be completely immersion breaking and so would the travel forever approach with repeating textures.
Just give me a little message in the game that says "turn back" or something.