Italy’s major cities all have great Metro Systems. The Metro (subway) is easy to use and an inexpensive way to travel around a large city. Maps exist at each Metro stop as well as in all tourist guides. Smart phone apps exist for each cities metros. You can use the app to find a place you want to go and then true app will determine where you are via GPS and map a route on the Metro for you. It will chow which train to take, which direction and all transfers to get you to your desired location.
The map below is an example of a Metro Map for Rome. You can see each line as a different color, end point and all intermediate stops.
George & Jo Anne