I don't know if I am the first to find this (probably not) but there is this glitch that I have found (no real point in it) so I figured I'd point it out for others to investigate it.

First I was on the Skuldafn mission, and I had no room for more loot, and there was no way to get back to drop stuff off, so I got restless and decided to mountain climb. I went a little to the right and behind where you start off at Skuldafn, and I proceeded randomly up the mountains.. Eventually I made it to the top and descended down and there was a giant plain of water, there was a tower randomly set in the middle, a random smoke pile somewhere throughout, and some small things.
It won't let you fast travel from ANYWHERE in Skuldafn, even outside. I am currently FAR north-northwest of Markarth, so literally they weren't kidding there's only one way in and out.

Like I said there is no point to this, however I just felt the need to point it out in case anyone else is interested.