At the base of the stairs, Bernini placed his equestrian statue of the Roman emperor Constantine the Great. It is meant to display the event, before the Battle of the Milvian Bridge when at Saxa Rubra north of Rome along the Tiber, Constantine sees a vision of the cross with the words In Hoc Signo Vinces (In this sign, you will conquer). The phrase appears prominently placed as a motto on a ribbon unfurled with a passion cross to its left, beneath a window over the Scala Regia, adjacent to the statue of Constantine. Emperors and other monarchs, having paid respects to the Pope, descended the Scala Regia, and would observe the light shining down through the window, with the motto, reminiscent of Constantine's vision, and be reminded to follow the Cross.