 The walls were decorated by Livio Agresti, Giorgio Vasari and Taddeo Zuccari.The frescoes depict momentous turning-points in the history of the Church, including the return of Pope Gregory XI from Avignon to Rome, the Battle of Lepanto, three panels narrating events surrounding the St. Bartholomew's Day massacre, the raising of the ban from Henry IV, the reconciliation of Pope Alexander III with Frederick Barbarossa and Peter II of Aragon offering the Kingdom to Pope Innocent III.The hall was originally used for the reception of princes and royal ambassadors, hence its name.