A Mapping Project: Small, Fortified Port

[CelestialBarbarian]

I'm wondering if anyone around here might have an interest in creating a map or maps for my D&D campaign world. I've been meaning to develop a small, fortified port town but with my poor spacio-mechanical skills haven't had the time and I'm not sure how well I could pull it off.

I’d like the a small, fortified port city to have a relatively small entrance to the harbor with a stone tower or stone rock outcropping towering over each side of the opening. If they’re rock they’d have stairways, rooms and windows carved in them to allow people to fire down at any ships that come near the opening to the harbor. A massive chain would run just under the surface to stop any unwanted ships from entering, but could be retracted to allow friendly vessels to enter (or leave). So in the rock on either side would have to be room for the chain to retract and for mechanisms to retract and extend the chain. (I’m not even sure if that’s physically possible, but it seems like a cool idea.) I was also thinking that there’s a “dungeon” under the ground level, for storage, access to the chain and mechanism, with a secret underwater entrance which characters might use to access the one or the other of the towers by swimming or using an Apparatus of Kwalish.

In my current campaign the pirate kingdom has seized the fortified port, and the king might send the party (which has reached 23rd-25th levels) to try to free it. I can’t really have them do it though until I have the physical location designed. So I don’t know if anybody here might help with that or not, but it would be great if they did. Thanks!