Cheapest Car Parking In Siena Over 5 Days In September

If you get overnight parking in Siena, try very hard to get secure overnight parking, like there's a guard or something.
And whether you do or don't, make sure you have not only insurance if the car is stolen, but also full CDW, and also insurance that will cover you in case the car is not stolen or structurally damaged but is trashed on the inside.
It wasn't my car but I've seen a car parked at the stadium near the historic center, wrecked by a guy in a truck trying to get out of the parking lot.
Some insurance is required and included in the rental in Italy, but you need to be sure of your coverage, and that you're covered to the max, doing overnight parking there.
An enclosed parking lot (in a building) may be best, not a big open lot like the stadium parking.

Here's Siena highlights:
http://www.ricksteves.com/europe/italy/siena

Cheapest?
At the train station.
With 2 euro you can park all day.
http://sienaparcheggi.com/it/1027/Parcheggio-La-Stazione.htm

Here are Siena highlights:
http://www.ricksteves.com/europe/italy/siena

If you park at the train station, you may want to do some research, before hand, to determine how much uphill walking, carrying everything in your car (don't leave it in the trunk), from the train station parking to your lodging.

Roberto & Kent:

Roberto: I saw the 2euro daily cost at the train station elsewhere on the internet, but I thought my interpretation of it was wrong -- why would the train station allow such cheap parking??? I thought the 2 euro was bound to mean per hour, which still is cheaper than most.
I hope you are right -- anyone else familiar with this., and can confirm???

Kent: My hotel does allow car pull-up to unload, but then you have to park wherever else you can find. Also we are traveling light, and don't anticipate buying a lot of stuff at the hilltop towns --- upon returning, won't have much to carry to hotel. Thanks.

Jim

Well, in Florence train station parking lot, about ten years ago, it was about 3 euros per hour overnight parking, and there was no daily max, 12 hours was 36 euros and 24 hours was 72 euros.
I don't know about Siena.

From the website:

PARCHEGGIO LA STAZIONE
E' la soluzione più pratica ed economica per raggiungere il centro storico e il Policlinico. Con 2 euro si parcheggia per tutto il giorno e la stazione ferroviaria è servita da collegamenti costanti garantiti dai mezzi pubblici. E' inoltre disponibile la risalita meccanizzata gratuita verso il centro.

Human translation provided by Roberto:

STATION PARKING
It's the most practical and economical way to reach the historical center and the Polyclinic Medical Center . With 2 euro one can park all day and the train station is served by frequent public transport connections. An escalator is also available to access the city center above for free.

And below on the same website page:
TARIFFAZIONE
Parking Fees:
€ 0,50/hr for the first hour
€ 2,00/ beyond the second hour and for the whole day

Jim,

Roberto: I saw the 2euro daily cost at the train station elsewhere on
the internet, but I thought my interpretation of it was wrong -- why
would the train station allow such cheap parking??? I thought the 2
euro was bound to mean per hour, which still is cheaper than most. I
hope you are right -- anyone else familiar with this., and can
confirm???

Regarding your comment above:

Roberto was born in Florence, Italy & travels there frequently... You can definitely trust his advice!

Here is a quote from Larry (from Carmel, CA) about Roberto before I knew who he was/is:

"Who is Roberto?", you ask. Clearly you are new to this forum! I suppose there are other Robertos in the world, even in Italy, and maybe even on this forum once in a while. But to us, Roberto is one of our most well-informed, savvy, witty and helpful participants, raised in Florence, now living in Northern California, but traveling back to Italy regularly. He seems to have more detailed information and guidance about most places in Italy than any guide book.

Keep in mind that you asked for the cheapest parking, so this may not be the BEST option... Roberto would know the answer to this though.

Happy trails!

Unless you are in love with your hotel, there are others that have parking. We stayed at Hotel Minerva in Via Garibaldi, garage parking onsite was €10 per day but that was three years ago. The hotel is at one of the city gates, ten minutes' walk to the Campo.