I recently started a new character, (have a previous one I was in the middle of when I installed HF), and right SE of Falkreath, on the road, there appears to be a fork in the road. I don't recall ever seeing it before, but it's probable that I just missed it, since Halldir's Cairn is on that road.
Anyway, I took the fork and proceeded westward until I came to an archway immediately SW of Halldir's Cairn, the same sort you see to the south of Riften (the entrance way to Morrowind, I think. I always get the message "You cannot go this way" whenever I try to pass through it.)
Well, this time, I went through the gateway, and kept going, and going, and going. Eventually the forest thinned out to just sparse pine trees, but then the trees ended and there was just dirt texture, rolling gray hills, huge basins, and high mountains. I kept going, and going, and going ever southward until the marker hit the edge of the map... and I was still going.
Then I literally fell off a cliff's edge right into some kind of gray, murky... underworld, I guess you would call it.
Has anyone else experienced this, or is it some kind of glitch on my part? Or something that existed before, but I never discovered? The area appears to be SW of Falkreath, extremely far south.
I'm thinking of loading up the previous character I still have a save for and checking to see if the glitch is there, but I wanted to see if anyone else has seen this.
It's... weird. I don't know if this is an area for a future DLC or what, but it's HUGE. I think you could probably fit a area the size of Whiterun Hold into it with room to spare.