The towers are roofed by two [Corner 4x4]s (I will use brackets around object names from here on out) and are the same dimensions the whole way through. They basically serve as staircases and pillars for the rest of the map.
I've traced out some movement paths with colored lines.
I also have a sweet Narrows re-imagining in progress with some beastly new features and a fresh new layout. I'll post pics after I take 'em later tonight.
7 hours later...
|Distilled (missing upper right still)|
|Distilled (missing village)|
|Bellows (Narrows on Steroids, bridge and one side done)|
|Bellows (Other side)|