Best rail route from Rome Airport to Siena

Pretty sure there is no train from FCO to Siena, you would have to go thru Termini- take the Leonardo Express

There is one direct train to Florence from FCO at 1:53 pm
There is also a bus from FCO to Siena- Flix bus I believe

A forum search should bring that info up

From Florence you would change to regional to Siena or take the bus as that will drop you in center at top of hill not at bottom where train station is

Are you using the official Trenitalia site?
https://www.trenitalia.com/content/tcom/en.html

Not sure if anyone else is having this problem but the Trenitalia website is way wonky for me today. Searches for one location to another just sit there and spin. Unusual.

Thanks for your informative response.
However, the T. site link you provided has some temporary issues.

Still, I found a schedule on other sites.

The Flix bus is direct from the airport to Siena in three hours. It states that the station is located, as follows:
Bus Station is located at the exit of Terminal 3 on the right ATTENTION! for line K340 operated by SIT - Società Italiana Trasporti platform is number 12.

I wonder how easy this station is to find in a huge airport?

Siena is not on main itineraries and is surrounded by hilly terrain on all sides, so all transportation is bound to be slow.
As for rail connections, the best thing is checking on the Trenitalia web site that will explain all the possibilities for a given date and time; please note the number of connections and total time. It is quite likely that the best choice is a fast train to Florence, to gain rapidly terrain direction north, then a train to Siena. In a sense you are backtracking as Siena is south of Florence, but the shorter alternatives may be slower.

A possible alternative may be bus service: there are buses from Roma Tiburtina to Siena (and this is likely to be the connection with less changes), from Florence to Siena (now leaving from a short distance from the Florence station, may be changing in the future), at some times even bus shuttles synchronized with Trenitalia trains (this service comes and goes on mysterious reasons). But I am afraid that bus are more difficult than trains to navigate.

Depending on schedules, the fastest way is probably the bus (Flixbus or Itabus) from the Tiburtina Bus Terminal, located next to the Tiburtina train station. Both Flixbus and Itabus have multiple runs every day. It’s a 3 hour bus ride.

By train you could take a fast train to Florence SMN (change at Termini or Tiburtina required in most cases except for one train in the PM), then a local regional train from SMN to Siena (or also an Autolinee Toscana bus). By train you need about 2.5h to get to Florence. The train journey from SMN to Siena is at least 90 min, to which you must add the waiting time. By bus it is 75 min but you must also add the 10 min walk to the bus terminal.

Another train possibility.
FCO → Roma Termini
Roma Termini → Chiusi-Chianciano Terme
Chiusi-Chianciano Terme → Siena

It seems like either option involves changing trains twice and the times are either equivalent or much longer (because of time waiting for long connections) using the non-fast trains. I would check the timings because you can't be sure when you are going to land and clear immigration in Rome and then allow for some slack when reviewing your options.

I think the fast train is the sensible, efficient choice - especially with luggage - versus the older, slower trains without reserved seats, modern toilets and a cafe car. I love the idea of riding the old pre-WWII train route but I don't know if the realities of that trip would live up to romance rolling off an international flight.

The Siena train station is outside town at the bottom of the hill and buses do drop you more in the city center. Since you will be landing in Florence SMN anyway I would opt for the train and take a cab from the station is you have luggage or the escalators up into town if you're into walking it. Otherwise you need to leave the train station and find the bus stop to Siena with your luggage and then manage that. For a day trip I think the bus is better but rolling through Florence I would take the train. Others may disagree.

Siena and Tuscany are amazing, have a great trip,
=Tod

you can't get to Siena from Rome -- oh of course you can -- but there is no convenient rail service without changes.

The bus from Florence to Siena leaves from the main bus station by SMN but also has at least one stop at Porta Romana. There might be others I am not aware. of.

Not sure if anyone else is having this problem but the Trenitalia website is way wonky for me today. Searches for one location to another just sit there and spin. Unusual.

The website is experiencing serious trouble today.
https://roma.corriere.it/notizie/cronaca/24_dicembre_17/trenitalia-sito-in-tilt-il-blackout-scatena-rabbia-e-proteste-dei-viaggiatori-prenotazioni-impossibili-per-ore-5e5c4eb6-dc8a-4c60-b319-22b93ab74xlk.shtml

Thanks, lachera; was hoping the problem wasn't with my browser.