Missing City Wall next to the port
I think it's just an oversight on the map, sort of like a typo, but there's no wall between the "Estuary of Roglaroon" and the port area of the city on the west side (upper left). It looks like you could pull up a boat and walk straight into town.
You could say there used to be a wall but it crumbled into the estuary, or the wall was never completed. The Invinceable Overlord, like the Spartans of old, feels no need of walls, so he never had it repaired/completed . . .
Perhaps the outer wall of the buildings along the shore forms a sort of stockade. It looks that way near the collapsed bridge, but there are major wide open paths into the city.
- Water-Rat Road (it has an army barracks at 358, near the entrance from the water)
- Fog Street (I'd make the undescribed 1, 11, and 12 here part of a stockade, the inner side of which is the Mermaid Tavern at 165)
- Two alleys around the Temple of the Toad (65, it must be part of the city's defenses, though the description doesn't mention that)
- By-Water Road (the Sea Captain's house at 64 must be a watch tower on the upper levels; at least it's vaguely round).