The portrait is in the Museum of the Castel Sant'Angelo in Rome, where it is attributed to the Roman painter Luca Longhi.

BBC: NEWS | Europe | Fresco fragment revives Papal scandal

There was also mention of noise from where the cardinals were locked in and the firing of cannons at Castel Sant' Angelo.

CNN: March 12, 2013 -- Updated 1404 GMT (2204 HKT)

The dungeons of the Castel Sant'Angelo, a papal fortress just near the Vatican, inspired the 18th Century Italian artist Giovanni Battista Piranesi to create his famous series of imaginary etchings of Roman prisons - I Carceri.

BBC: Magazine