Samuel Ball Platner: A Topographical Dictionary of Ancient Rome (1929), haettu 9.1.2009 "The Piazza Navona, the largest in the city, now called officially Circo Agonale, preserves almost exactly the shape and size of the stadium. The piazza itself corresponds closely with the arena, the length of which seems to have been about 250 metres, and the surrounding buildings stand on the ruins of the cavea."
