Visitors can see the cells in which a number of historical figures were incarcerated, different rooms that functioned as a Papal residence, decorated with perfectly preserved frescoes from the Renaissance period, as well as the extensive collection of weapons.

On the upper floor there is a large terrace where you have a beautiful view on Rome 

The castle/prison was used by Puccini for his opera 'Tosca', as the setting for the third act, when the heroine leaps to her death from the Castel's ramparts.

For more detailed informations, see website