You can have a combined ticket and the library is just steps away from the duomo. It is a must when you visit SIena. The wonderful colered books to see, the frescos on the wall are just incredible.
The Piccolomini Library is housed within the Duomo. On TripAdvisor, The Duomo is listed as the Siena Cathedral and is the #2 "Things to do in Siena". If you go to that TripAdvisor listing, you will see a yellow button... More
The Piccolomini Library is housed within the Duomo. On TripAdvisor, The Duomo is listed as the Siena Cathedral and is the #2 "Things to do in Siena". If you go to that TripAdvisor listing, you will see a yellow button linking you to the Duomo of Siena Complex: Skip-the-line Entry Ticket, which is approx. $13 and up cost. There's also a yellow button link to the Viator Skip the Line: Siena Duomo and City Walking Tour, cost approx. $33/pp. I booked this tour ahead of time and my entrance to the Duomo was included in the cost. It was a great tour with Sylvia. The Siena Cathedral listing also has a website link to the official Duomo ticket office (the operaduomo site) where you can make inquiries via email or even book tickets online. The Piccolomini Library, and the Duomo it's housed in, were two of my favorites on the tour I took. Since I was part of a late March skip the line tour, I can't speak about wait times, because we only had a 5 minute wait while our tour guide picked up our passes in the ticket office. We then simply walked into the Duomo without queuing. Italy tourist sites can be crowded anytime you go, I would book a "skip the line" ticket or tour ahead of time through one of methods I describe above. However, if you need more flexibility, then take a look at TripAdvisor reviewer, pingaroo, who talks about purchasing a skip the line entrance pass to the complex for 13 Euro, plus 7 Euro more for the Gate of Heaven Tour. Pingaroo purchased the tickets upon arrival in Siena on a Sat in September 2016. The pingaroo review is on the Siena Cathedral review page listed under "Must do Gate of Heaven tour" posted on March 30 2017. Hope this helps :)