car pick up & drop off locations Rome-Florence

If I was going to do that trip over, I'd take a train up to Orvieto and spend one night there. It's a great hilltown, and very popular as a place to pickup and turn in rental cars. And Orvieto's just 70 minutes from Rome Termini on the train.

The Orvieto Hertz location is across the street from the train station. The drive up to Siena is just about 90 minutes on very good roads/motorways.

I hope your Siena hotel/accommodations have parking, as it's a very difficult city to find parking in.

It's a straight shot north into Florence from Siena. Hertz' Sansovino location is a couple of miles NW of the Florence train station, and you can catch a cab to your hotel. You can easily avoid the ZTL by turning the car in there.

In Florence you will probably want to avoid driving the car into or near the historic center, because of something in Florence called ZTL's.

Spending a night in Orvieto is something we'll have to consider. Would have to change our Sienna hotel reservation.
Is it worth turning in the car in Sienna and taking the train to Florence, or just drive to the drop off point in Florence near the train station?

We rented a car last June from Avis at Termini Station in Rome. I had reserved a car from Hertz and when we got there the line was 2 to 3 hours long. We were forget this we are not waiting so I canceled reservation when I was on the line and went over to Avis who had no line. Got a car right away. We returned it to Florence and I cant remember the name of the street but it was near the train station. Just do a google car rental search, that is what I did. Also, it was a very easy drive not as crazy as what people tell you.

Pick up in Rome at the Tiburtina station. From there you are next to the freeway entrance (Tangenziale est, A24).
I don't know where you are staying Siena, but they have traffic restrictions in the historical center, therefore make sure you choose your accommodations in areas that are car accessible and preferably with parking in the premises.
If you have a car, why not drive to Florence and return the car there?
Where to return to avoid the ZTL depends on the rental company:
AVIS at Florence airport.
Hertz, at via Sansovino
Europcar at via Forlanini.
Otherwise all have offices downtown at Borgo Ognissanti. The company will enter your car in the city website to avoid being ticketed.
Select your choices with a consolidator:
www.autoeurope.com
www.kemwel.com
Check prices with both.

We're staying at the Athena Hotel in Siena. I believe that they have parking available?
If I return to Florence in the city the car rental will handle the no drive zone issue for me?

Yes, I checked and the hotel Athena has a parking garage. To reach it the freeway exit is Siena Ovest (Ovest=West). Then you need to take the via Massetana to Porta San Marco. As you pass under the Porta (City Gate) turn immediately to the left and drive along the inside of the city walls. That road is accessible.
For Florence you may not even need the rental company to notify the city that you entered the ZTL (via website). That will be necessary only if you rent at the Europcar on Borgo Ognissanti. All other offices can be reached without going through a ZTL camera. The ZTL is a problem only when you enter it, not when you drive out of it, therefore your pick up location can be anywhere. When you return it, if you choose a return location at Borgo Ognissanti, you might have to go through a ZTL camera, depending on which company you choose. Europcar on Borgo Ognissanti can be reached only after going through a camera, therefore the rental car company will need to be notified that they have to enter your lic. plate number in the City website. All other companies can be reached without going through the camera, because they are in a section of Borgo Ognissanti that can be reached through another route.
Your next move is to rent a car (use the consolidators I gave you), then we can discuss how to get back to a return location without fear of incurring into the ZTL.
Florence is where I was born and lived most of my life, so I know it like my back pocket. I'll get you in and out without harm, don't worry.

Roberto, We are renting from Hertz. We are returning the car to FLORENCE DOWNTOWN OFFICE
VIA DEL SANSOVINO 53. We are staying at Hotel Casci in Florence.

Is that the best place to return the car? Or should I return to a different Hertz office in Florence?
Thanks

We have done this many times. The Athena does have parking; be sure you have made arrangements for it with your reservation because it has very little parking. Also ask for a high room facing the countryside -- really great views. The hotel is well located for the walk into the Campo and is near one of the gates in the wall for leaving to tour elsewhere. Siena is a good size city which makes it a bit less ideal for day tripping -- you have lots of city to get through to get to the countryside but it is a stunning historic center and a lovely place to spend time.

We always drop the car at the airport because in Florence the odds of a very expensive ticket are enormous if returning the car downtown. Make a mistake and circle the block and you can end up owing several tickets in a few minutes. It is not only the ZTL issue but also bus lanes and other hazards you are not used to navigating. Do not think the rental agency will 'take care of this for us.' Fat chance. They take care of it by charging you 50 Euro or so just to provide your address and contact information to the police. You might make it through the gauntlet with careful driving instructions, but many people don't.