Pompey's pillar is one of the biggest memorial column in Egypt. It a huge column of red granite stood at the temple of the Serapis, it was once a magnificent structure rivaling the Soma and the Caesareum. Nearby are subterranean galleries where sacred Apis bulls were buried, and three sphinxes, and a“Nilometer” for measuring the annual Nile Floods. After his defeat by Julius Caesar in the civil war, Pompey fled to Egypt where he was murdered in 48 BC;mediaeval travelers later believed he must be buried here. The temple was also a library of religious texts.
The pillar, with its circumference of 9 metres and height of 25 metres, was added to the complex in 293 CE, in honour of Diocletian. Diocletain captured Alexandria after it had been under siege. The Arabs called it "Amoud el-Sawari", Column of the Horsemen. The Pillar is the tallest ancient monument in Alexandria. The temple was destroyed by fanatical Christians in 391 CE, and they did a thorough job. The great pillar, however survived, together with a few sphinxes.