Pisa is a small town about an hour outside of Florence. A day trip is all the time I would recommend spending in Pisa.
If you are renting a car, it is basically a straight shot from Florence on one of the major interstates. Google maps is the best way to go when you don’t want to use your data and don’t have wifi on the roads.
There is a popular train route that takes you to Pisa from Florence. You can purchase tickets online, they leave several times per day.
What to do there:
The tower of Pisa. Yes, the Italians have a structure that appears to be “leaning” due to apparent foundation problems.
At the tower, you are able to walk up the top and see panoramic views, for a small price.
Gelato! At every corner, its Italy, Gelato can not be passed.
Donor kebab. Shaved meat from a rotisserie, they make into a popular sandwich.