Pompay’s pillar is the biggest memorial column in Egypt. It is an approximately 25m red Aswan granite column with a circumference of 9m that was constructed in honor of the Emperor Diocletain. Originally from 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. 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, and that the capital atop the corner served as a container for his head. In fact, the pillar was raised in honor of Diocletain at the very end of the 4th century. 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.