The following links and resources provide a useful set of visitor attractions in Siena, Italy.
External Content for Siena Attractions While many of these sites are provided by tour companies of some kind, they include useful lists of the most visited places in Siena. Some are more detailed and diverse than others.
What to Do and See in Siena, by Italy Explained
Siena Tourist Attractions, by Siena Italy Tourist Information and Travel Guide
15 Best Things to Do in Siena, by the Crazy Tourist
Siena Attractions, by Lonely Planet
Things to Do in Siena, by Visit A City
Ten Things Not to be Missed in Siena, by Visittuscany.com
Visiting Siena in a Day, by Discover Tuscany
Twelve Best Things to do in Siena, by Touropia
Things to Do in Siena, by TripAdvisor
The Siena Visitor 