Siena can be easily reached without a car. The nearest airports to Siena are in Florence, Pisa and Rome (in that order) and there are good bus and train connections from all three cities. Once you arrive in Siena, exploring the city is actually best done without a car. Below I explain how. Here's our suggested itinerary for spending a day in Siena and seeing the main sights, although we highly recommend you slow down your itinerary, spend a night or two here and enjoy all of the treasures Siena has to offer.
Getting to Siena from Florence
Coming from Florence, you can either take the bus or the train. If you have landed at the airport in Florence, you will need to take the shuttle bus (more info here) which leaves just outside the airport and takes you to the main train station Santa Maria Novella. Both buses and trains to Siena leave from here.
The bus station in Florence is right in from of the SMN train station, but may be a bit hard to find at first as it is down a short side street and hidden within the block. The easiest way to find it is to ask directions for "auto-stazione" (bus station) but you can also map the address: Via Santa Caterina da Siena. It is the short street that leads you past Bar Deanna to Via della Scala if you are exiting the train station and face Piazza della Stazione/the back of the church of Santa Maria Novella.
There are two different buses to Siena run by Tiemme: Rapida (the fast bus) and Ordinaria (ordinary or slower bus). We obviously recommend you take the Rapida, line 131R, since it is a non-stop between Florence and Siena, lasting about 1 hour and 15 minutes. The Ordinaria, line 131O, stops in two villages on the way and thus takes 1 hour and 30 minutes, the two stops being Poggibonsi and Colle Val d'Elsa (in case you do need to go there, this is the bus to take). The bus has adequate storage space for luggage underneath, just let the driver know you need the luggage space opened up.
You arrive in Siena at Piazza Gramsci/Viale Tozzi, which is closer to the center than the train station in Siena. Underneath the piazza, in the "sottopassaggio della Lizza", is the bus station where you can buy tickets for the way back (there is also an automatic machine on the piazza, if the office were to be closed), ask for information and find baggage storage (with over the counter service, stored behind the ticket windows), restrooms and an ATM machine.
Timetable: Usually two buses leave every hour. For an updated schedule click here: http://www.tiemmespa.it/index.php/Viaggia-con-noi/Orari-e-linee/Siena/Extraurbano (note the number is the same, what changes is an R or O for the two times).
Cost: A one-way ticket is € 7.80 if you buy it at the station beforehand and € 10 if you buy it on the bus.
* Always remember to validate your ticket by getting it stamped in the machine as you board the bus. This puts date and time on it, making it valid. If you forget to do so, you can be fined for traveling with an unstamped ticket (this is true for all regional trains as well).
UPDATE 2018: Flixbus now offers a connection between Florence and Siena as well but the departure station in Florence is Villa Costanza, the end line of the T1 tramline (also a handy, affordable parking lot). So first you need to get to Villa Costanza if you're in the center of Florence and from there take the bus - which just takes 1 hour and costs €5 (plus, the tram ticket costs €1.50). Just another possibility to consider, depending on where you start in Florence.
If you travel with small children you might find the train more comfortable as there is more space for the stroller and for them to walk around. There are two trains per hour, one is direct and takes you to Siena in 1 hour and 30 minutes. The other one takes you to Empoli where you will have to make a train change and the whole trip thus takes 1 hour and 45 minutes.
The train station is at the bottom of a hill in Siena, so to get to the historical center you might want to catch a bus to Piazza del Sale/Viale Garibaldi or Viale Tozzi/Piazza Gramsci - there are many buses that go that way and get you up the hill close and near to Via Banchi di Sopra, from which you can walk to Piazza del Campo.
* There is also a mobile escalator from the train station area that takes up up the hill to Via Vittorio Emanule II which is near Porta Camollia. You can take that street all the way to the center, right behind Piazza del Campo
Timetable: You can search the schedule for this and all other routes on the TrenItalia website here: http://www.trenitalia.com/.
Cost: A one-way ticket is € 8.60 and can be purchased at the station either at the ticket office or through the automatic machines.
* Always remember to validate your ticket by getting it stamped in the machine at the platform before entering the train.
Getting from Pisa to Siena
Coming from Pisa you can also travel by either bus or train.
The bus leaves directly from the airport, with a stop and bus change in Florence. The trip takes about 1 hour and 10 minutes between Pisa and Florence, and then about the fast buses from Florence to Siena about another hour and 15 minutes to make the trip be about 2.5 hours.
Timetable: From the end of March 2014, service has been boosted to offer up 10-12 buses per day from Pisa airport passing through and changing bus in Florence (whereas it used to be just 1 bus per day before, so this is an improvement). Check this link for the updated timetable.
Cost: € 15 one way, € 28 round trip.
If you arrive at Pisa airport you can catch the PisaMover shuttle bus to the main Pisa train station. It leaves every 10 minutes from the airport and the trip takes 8 minutes. Trains leave approximately two times per hour from the Centrale station to Siena. You will have to change in Empoli and the whole trip lasts about 1 hour and 50 minutes.
Cost: € 11.30 - check time tables at the link above
Getting from Rome to Siena
From Rome, you can also either take the bus or the train to Siena. The bus leaves more frequently, is easier and shorter than if you travel by train. Both buses and trains leave from Roma Tiburtina. To travel from the Rome airport to Roma Tiburtina, you will also have to take a train – the platform is inside the airport. This part of the trip costs € 11 and lasts 30 minutes.
The ride with SENA takes 2 hours and 45 minutes. The first stop is at the train station in Siena and then at the bus station in the center so you can get off at the one most convenient to you.
Timetable: The bus leaves approximately every two hours. To find a bus, check http://www.sena.it/Home/78-1-en.html
Cost: € 22
FlixBus also now goes from Rome (Tiburtina station) to Siena, and costs less, from €8-12, depending on time of day, and also takes 2.5-3 hours with various stops in Siena, including the bus station in Piazza Gramsci and the train station. Check them both sites out to see which one better matches your schedule.
The trains leave less frequently, you will need to change in Chiusi and depending on the waiting time in Chiusi, the whole trip lasts between 3 and 4 hours. Another option is to head to Florence, then change trains there as those might end up being "faster", relatively speaking.
Cost: The cost of the train varies, but is approximately € 20.
---> If you need to get to ROME to the Fiumicino airport from Siena, BUS+TRAIN is the best way to go! Just train takes a long time, as there is no direct connection so you either have to go to Florence or to Chiusi and change trains before continuing on. Right now, the best solution is to take FLIXBUS from Siena to Rome Tiburtina train station and from there you can continue by train to Rome's Fiumicino airport. Take a look at timetables for Flixbus here. You can check train timetables on the trenitalia.com website.
Getting around in Siena without a car
If you are only in Siena for a shorter period, the only bus you will need is the one taking you from the train station to the city center (if you arrive by train). The rest of the city can easily be reached and visited by foot.
Siena Train Station
The train station in Siena is situated about 2 km north of the city center. It takes around 20 minutes to walk to the center and it’s uphill. Alternatively, we recommend you can catch a bus; all buses from the station pass through the center and will take you there in 5 minutes. Get off the bus at either Piazza del Sale or Piazza Gramsci. You can cut the walk short by taking an eletric escalator from near the station up the hill, but that still takes you to one corner of the city walls from which you need to walk.
Siena Bus Station
Arriving by bus takes you to the center of Siena, closer to all of the main sights than the train station. Siena’s bus station is at Piazza Gramsci from where you can walk to all the important sights in the city.
Check out the map below to see the relative distances between Piazza del Campo (where you want to go) to where the bus and train stations are.