Siege tower. This engraving, published in 1785, shows a siege tower used to attack city walls in Ancient Greece. Pushed from behind, it moved over planks on rollers made from logs. Its bottom level was furnished with a battering ram, while the upper stories held warriors with catapults and dart-casters. The purpose of this machine was to move attackers safely up to a city's walls, and allow them to fight with defenders at the same level. The illustration resembles descriptions of the gigantic Helepolis ( City-taker ) built by the siege engineers of Demetrius Poliorcites (king of Macedonia) for his unsuccessful attack on the island of Rhodes in 305-304 B.C.