Dominique Ehrhard is a favourite game designer of mine, not least for the sublime Condottiere. He is also to be equally appreciated for his artistic abilities (he created the art work for Condottiere and Serenissima). Serenissima is an early design, originally published in 1996, it is both a game that retains a lot of enjoyment, and a game that feels it's age compared to the slick mechanical designs of today.
I should note that the version of Serenissima I am talking about is the older one. A newer version (2nd ed) was published by Ystari and Asmodee, and from everything I have read the newer version brings the old game back with revised game mechanics.
In any case, Serenissima is a highly enjoyable mix of travelling salesman problems mixed with the tension of defensive blockading and attack. It is a highly enjoyable roller coaster, where players are doing their utmost to monopolise trade and get their goods through to the ports that will assure them the most profit.
Clever use of investments is key, as is making sure you appropriate enough varied ports to give you access to a variety of goods. The use of ships loaded with sailors to blockade sea zones and attack the opponent is also something that requires consideration. The game can swing from the mind bending complexity of working out where your ships can move and what they can trade, to an arms race to decide the fate of a port or trade ship.
All in all the game was highly enjoyable, and has made me interested in seeing how the second edition plays.