Road trip from Florence to Rome

Orvieto is a favorite of many on this forum. The cathedral is a Wow.

Anymore, Orvieto only has one or two rental offices, so make sure you can actually drop off there, but if it works, sure, sounds like a good plan.

It’s a lot for one day, especially with kids. You’ll have to add in lunch, all while worrying about your belongings in the trunk during stops. Do your kids get car sick? Not the time you’ll want to find out!
Saturnia’s water is quite smelly (the sulfur), so you’ll likely want to make use of the shower facilities at the site.
I think I’d consider just doing Orvieto by train.

It’s a great plan, but only if you planned to do it in a few days, stopping in some locations for the night and using those locations as a base for day trips. If you are planning to drive the entire route in one day, then I would have to dissuade you, because there will be the following issues to consider:
1. The drive is longer than you think. It’s a 3.5-4 hour drive from Florence to Rome, assuming you make no stops except for gas and restroom) and drive on the freeway at al least 120 km/h (75 mph) whenever traffic permits. If you take the regular highway, like the Via Cassia (SS2), it will take you 6-7 hours even just stopping for gas and restroom. Also consider the time necessary for the car pickup paperwork and the time necessary to go to the rental agency and driving out of the city. Driving from Florence to Saturnia is a 3.5 hour journey at least (plus pit stops), given the nature of the road. From Saturnia to Orvieto is another couple of hour drive on very curvy roads. Then the drive from Orvieto to Rome or Rome airport is another two hours in the freeway (only Hertz is in Orvieto, if you return there). So if you do all of this in a day, where is the time for sightseeing anything?
2. Making a stop along the way, en route to Rome, means having to leave your luggage unattended inside the trunk while you visit an intermediate town or the Saturnia springs, which I would not consider a good idea, even though rural Italy is safer than the average American town. Having your rental car smashed to grab one of your bags would ruin the rest of your trip.

So if you plan to visit something on the way to Rome in one day, you should consider sticking to the train, stop in Orvieto, leave your luggage at the station (a shop at the station or across the tracks in the big parking lot offers luggage storage), visit Orvieto for a few hours, then proceed to Rome by train.

Ok, I’m receptive to these opinions - thank you! Is there any scenario that makes going to Saturnia baths a better option than Orvieto? I think I know the answer, but I’m so curious about the baths! For now, I’ll probably stick to Orvieto but I’d love to make a visit to the baths for something a little different.

Oh sure you can do either/or if that appeals to you more. I frankly didn’t love it because of course the photos all show a paradise but in person you have a lot of humanity taking dips in various states of undress. Maybe in cooler April you might luck out. My spouse is allergic to crowds so we did not give it much more time than a foot soak.
Nearby there there are many sites I think kids would find interesting. Pitigliano is gorgeous and there are “vie cave” Etruscan sites throughout the area.
You do still have to worry about your stuff in your trunk, but that’s more of an “abundance of caution” kind of thing.

It’s two totally different experiences.
Orvieto is an ancient walled hill town with a famous cathedral. It’s an historic art town. If that is your choice, the train is the better choice.

The baths of Saturnia (watermill falls) is a sulphuric spring spa where people soak in the natural looking pools of a volcanic river (the pools were remodeled with travertine to look like natural pools after a flood in 2014 destroyed the pool terraces). There is also a famous spa resort called Terme di Saturnia where they have pools, massages, etc. for a day fee.

The only way to Saturnia is by rental car. It’s a long 3.5-4 hour drive, partially on curvy roads. The metered (dirt) parking lot at the Watermill Falls (Cascate del Mulino) is about 200-300 yards away . It’s not a guarded lot. The falls get crowded (I was there last in July 2022 and July 2024, but in April it will be just as crowded if not more. The Terme di Saturnia spa hotel and resort is nearby. They have a private parking lot. I don’t know what they charge for the day nowadays, the last time I went to the hotel was a long time ago. From Saturnia it will be faster to drive to Rome taking the Aurelia freeway along the coast. The freeway passes near the FCO airport, if you want to return the car at the airport.

In late June 2024, we took the train from Florence to Chiusi, walked 50 steps across the street to pick up our car, (and stayed nearby in a sleepy town Cetona, shout out to La Locanda di Anita). But we went to Saturnia & Orvieto in an afternoon and it was lovely. ** bring cheap water shoes for the baths.
After 3 nights in the town, we returned the car and got right back on the train to Rome, so easy. I would 100% ditch the car before going to Rome. You can swim in the baths a bit downstream, it opens up slightly compared to the little bath parts. Can I tell you, the entire time we drove around the hill towns, we were practically the only ones on the road. It was mind boggling, just rolling hills and open backroads. So magical.

Last year, I picked my daughters up in Rome in the rental car and we drove to Florence stopping at Orvieto (only) along the way. That didn't feel rushed and they really enjoyed Orvieto, somewhat as a contrast to the crowds in Florence & Rome.