Make your way to the Conciergerie, one of Paris' most important monuments, located on the banks of the Seine River. Exchange your admission voucher for your skip-the-line ticket and proceed directly inside, past the waiting crowds.
Explore the monument at your own pace on a self-guided tour. Tour booklets are available in 11 languages, and will take you through the medieval Hall of the Soldiers, the Guards Room, and the kitchens built in the 14th century for King John the Good.
See the cell where Marie Antoinette was imprisoned, among cells that housed other famous prisoners during the French Revolution. Wander through Sainte-Chapelle to see the stained glass windows and the oldest public clock in Paris, which has been showing locals the time since 1371.