The Chiesa di San Lorenzo in Palatio ad Sancta Sanctorum, known simply as the Sancta Sanctorum, is a Catholic chapel in Rome featuring the Scala Sancta of the Lateran Palace. It was the original private chapel of the papacy before it moved to Avignon, and later to the Apostolic Palace. The chapel is the only building from the old Lateran Palace that was not d…The Chiesa di San Lorenzo in Palatio ad Sancta Sanctorum, known simply as the Sancta Sanctorum, is a Catholic chapel in Rome featuring the Scala Sancta of the Lateran Palace. It was the original private chapel of the papacy before it moved to Avignon, and later to the Apostolic Palace. The chapel is the only building from the old Lateran Palace that was not destroyed during its reconstruction.