Thank you for your responses! It is nice if my work can actually inspire others (I was inspired by many many architects in various forums...)
I've been having the same idea for years. (and I purchase / collect) Playmobil for that purpose. But I can't imagine my portcity will grow soo big and nice as yours. Though the fleet might turn into an Armada... 
I first had the city surrounded by a wall also at the harbor-facing side (see first pic, front side). Now I decided to have the city more open (using quite a few double arches and having more houses/storage facing the harbor) - so people can actually bring their goods and merchandise into the city without the hassle of passing a gate. This might result in a less protected city - but the outer walls are more a defense against troops coming from land.
The Licorne is welcome to let go anchor at the harbor (that's why it must be so long...)
How did you take care of the flooring?
Do you refer to Gioginetto's question?
Great Steck work !!. How do you keep the double floors hanging on your outer double walls ? That was a problem i enountered in my mediaval city ...

This is in fact a problem BUT if you are using the floors shown in the image, you will not have these issues.
image:
http://playmodb.org/cgi-bin/showpart.pl?partnum=30-03-9810Alternatively, you could use these:
http://playmodb.org/cgi-bin/showpart.pl?partnum=30-02-8480and use in between 2 of those:
http://playmodb.org/cgi-bin/showpart.pl?partnum=30-02-9150hauden_lukas