Writing "Ab Urbis Condita" in the 1st century BC, Livy says "the Circus, now called Maximus...." and goes on to describe seating platforms 12 ft high. https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0151%3Abook%3D1%3Achapter%3D35