If we're deciding on where to put the depot, it needs to be protected somehow. Any structure would suffice, as long as it could keep things out in emergency.
Well, with Trade depot we are getting quite ahead of ourselves. as you can see on
map: we do not actually have neither city, nor village, not even keep, so placing trade depot is not actually our first priority. We should also keep in mind that while it would be nice to protect merchants from hostiles, it would also be nice to please our insane old king with a "open" fortress, without enclosing large portions of our settlement with impregnable walls.
While it should be ok to have impregnable castle for our more valuable citizens (and here I mean nobles, senators and such), it can be quite an overreaction to put impregnable defenses around more common areas, like, for example, marketplace.
Although I think it is ok to have a city wall too, but with clear and always-open highways for trade and othe civilian traffic to flow freely.
While it is hard to predict the size oh the city, and thus hard to draft any particular plans for city walls, I think we can somewhat estimate the size of initial keep, and therefore lay plans for castle construction and design. It would be nice if Fortification Commissioner could layout plans as to where should keep be, how many gates should it have, what is the architecture of it's main structures and how large should it be. This way we will be able to start settling common warves around the keep, and save ourselves from the need to dismantle their shacks later.
The cliff to the north of longhall looks rather promising and scenic to put keep there.