User blog comment:Buginmyeye/Dunwall City Map/@comment-84.92.131.50-20130113143039/@comment-5987961-20130114054121

The gate leads to a draw bridge that goes to the prison. I didn't realize this until I saw this image yesterday in the Coldridge_Prison page.

So this means that it is to the south Dunwall tower. Assuming the mouth of the river is South.