Il ponte delle Gabelle

Il Ponte delle Gabelle (Excises Bridge) located in Via San Marco, is just a hint on how Milan was filled with canals. Besides the bridge indeed, you can see the dam that regulated both water level and flow… Do you know what a dam is?
 
Keeping it simple, is nothing but a barrier, a wall or a main door you can open and close to allow navigability in any river… This is an innovative system that we still use today; just think that this one was designed by Leonardo da Vinci more than 600 years ago! Why was this bridge called like this? Gabelle (excises in English) were goods duties, that is to say, every time a boat passed under a bridge an excise was required!