I've spotted several Dwemer lifts dotting the landscape in the region where the borders of The Pale, Eastmarch, and Winterhold all meet... All locked up tight, not even any sort of door or switch to frob.

...Are these all return lifts from Blackreach? I noticed several down there but only took the quick exit right after the Elder Scroll reading apparatus when I was after the Scroll inside it.

They all either go to blackreach, or another ruin with a door to blackreach nearby.

Several also have to have an associated quest to start from the outside (unless you went in from the other side in blackreach)

Some are exit only, with the entrance being some dwemer ruins nearby.