Pompey's Pillar is a Roman triumphal column in Alexandria, Egypt, and the largest of its type constructed outside of the imperial capitals of Rome and Constantinople. The only known free-standing column in Roman Egypt which was not composed of drums. it is one of the largest ancient monoliths and one of the largest monolithic columns ever erected. The monolithic column shaft measures 20.46 m in height with a diameter of 2.71 m at its base.