Had the same issue. I opened the Map in the editor and it appears to be some kind of artifact from Move-It (?). For this i deleted some part of the "Wiggely Road" that leads up the mountain, which solved the problem for me.

And yes, awsome map, great work on the glaciers, too!

I have no clue how i came there as I never build any road on this location, my guess its a cities skylines bug or maybe something went wrong when I saved the map.
Sadly me and others tried to have it gone but nothing help even a blank map with zero mods it was still there. Its literally a ghost haunting my map. maybe Ghost busters can help