I am renting a car in Venice and returning it at the end of July in Rome. I have to return the car to Termini. Will I have trouble driving into the city to do so? Am I restricted by the limited driving zone?
Termini is "north" of most of the restricted driving zones. If you're heading south - and staying on main roads - you should not have any problems.
When you return at Termini, almost all the rental agencies are at the same parking garage. To get there, FROM DIRECTLY in front of Termini... head toward the Left side of the building on Viale Enrico de Nicloa.. TURN RIGHT onto Via Marsala... and head down the LEFT side of the Termini Station on this road....
At the first RIGHT turn you can make there are two sets of tunnels on your right - TAKE THE 2nd TUNNEL entrance... Both of these are Sottapassaggio A. Pettenelli - THE SAME ONE-WAY ROAD - but the right tunnel allows you to only make a right turn on Via Giovanni Giolitti, taking you back to Termini - you need the LEFT (or 2nd) tunnel so you can make a LEFT on Via Giovanni Giolitti, as that's where the parking garage is... As soon as you make that LEFT on Via Giovanni Giolitti you will see the parking garage and rental car signage directly in front of you!
Hope that helps,
Ciao,
Ron