I'll be in Siena for several weeks for a class, and looking for must see recommendations for my weekends off or any special sites in Siena you'd recommend. I've been to Tuscany a few years ago so have been to a few basic sites already (Florence, Pienza, Montalcino - Wineries)
Two of our favorite "unknown" places to visit in Siena are the State Archives (Archivio di Stato) located in the Palazzo Piccoloimi on Banchi di Sotto across from the University and the L'Aqua Museo just outside the gates. Both seem to be well kept secrets but well worth visiting. The L'Aqua Museo is located in a part of the underground structures excavated in the 1200's to provide a source of water to Siena. The history is very interesting. And if you are by chance a lover of libraries, the Archives are a fascinating place to visit. The fiscal records of the city dating back hundreds of years are found there.
One additional recommendation would be a day trip to Volterra. There are some beautiful old ruins there and many shops featuring items made from alabaster.
We will be in Siena this May for the first time so I don't have first-hand experience. After exploring Siena for a day, our plan is to visit Volterra and San Gimingnano.
Thanks for the suggestions. I've added Volterra and San Gimigniano to our list!
Monteriggioni (B)
Colle Val D'Elsa (B)
Montepulciano (B)
Buonconvento (T)
Certaldo (T)
Barberino Val D'Elsa (T+B)
Castellina in Chianti (B)
(B) by bus
(T) by train