Why isn't there a direct landroute between these two major cities? You can see Sunhold when you're standing on the bridge leading to Alinor palace. Feels unrealistic that the Altmer wouldn't build a road between them.
Ever heard of the trouble people in the real world have whenever they want to build just a short road through some nature reserve or similar area? I could imagine the high elves being even worse at this. Might even be a strategic choice to avoid the capital being easily accessible from all sides (and Sunhold as well).