The Tower of David and the Hippicus Tower were built to protect the chief entrance to the Old City of Jerusalem. The Hippicus was named after Hippicus, a friend of Herod the Roman King of Judaea who died in battle. This tower was one of Herod's three famous towers. The other two were the Phasael Tower and the Miriamne Tower.
When the Romans destroyed Jerusalem in 70 CE, only Phasael Tower was able to withstand the invasion. During the Byzantine period, this tower and the Citadel was called the Tower of David, somewhat erroneously, as the Byzantines thought the hill to be Mount Zion and the citadel to be David's Palace. The Citadel was rebuilt during Muslim and Crusader rule, it was Malik al-Nasir, the Mamluk sultan who gave the shape to the actual citadel in 1310. The minaret was added in the 17th century, and in the 19th century became known as "Tower of David."