Many cruise itineraries will list Pisa and/or Florence, but what they really mean is Livorno. The actual port is in Livorno, which is the cruise gateway to Pisa and Florence. Pisa is about a 30-40 minute drive from Livorno and Florence is about an hour.
Within the port town of Livorno itself there is a little bit of walking around to do, but not a whole lot to see. It is a fairly recently established town by Italian standards (meaning it's still older than any cities in the US but isn't all that old compared to other Italian cities) and it isn't packed with the history and landmarks of the better known cities.
Livorno does call itself New Venice, because there is a canal running through part of the city. But don't be fooled, it is nothing even remotely like Venice and there isn't all that much to see there. There are no gondolas and the city isn't built on it. The canal is really just a normal canal.