With the Harbour Master DLC you can enhance Port Royale 3 with six completely new building types, several decoration objects for your cities and with an economic adviser, who will give you useful hints. In addition you will now have more control over the defence of your cities and you will be able to build ships on your own!
Six new buildings (e.g. embassy or fire department)
Decoration objects like plants, statues or several pavings
More control over the extension of the defence lines
Economic adviser who gives useful advice when necessary
Build your own ships