"The Column of Marcus Aurelius, Rome, which stands in the Piazza Colonna, commemorates the Emperor's victory on the Danube. It resembles Trajan's column and formerly stood in front of a temple dedicated to the Emperor. The marble pedestal is surmounted by a shaft 29.64m high and 4.01m in diameter, carved with remarkable spiral reliefs. The top is reached by 197 steps and was crowned by the statue of Marcus Aurelius till it was replaced (A.D. 1589) in the time of Pope Sixtus V by the existing statue of S. Paul. The spiral band winds round the column in twenty tiers, and represents the campaigns of Marcus Aurelius against the German tribes north of the Danube."
----Palmes, J.C. (Ed.). (1975). Sir Banister Fletcher's: A History of Architecture. 18th ed. New York: Charles Scribner's Sons. p. 327.