The Helepolis was essentially a large tapered tower, with each side about 130 feet high, and 65 feet wide that was manually pushed into battle. It rested on eight wheels, each 15 feet high and also had casters, to allow lateral movement as well as direct. The three exposed sides were rendered fireproof with iron plates, and stories divided the interior, connected by two broad flights of stairs, one for ascent and one for descent. The machine weighed 160 tons, and required 3,400 men working in relays to move it, 200 turning a large capstan driving the wheels via a belt, and the rest pushing from behind. The casters permitted lateral movement, so the entire apparatus could be steered towards the desired attack point, while always keeping the siege engines inside aimed at the walls, and the protective body of the machine directly between the city walls and the men pushing behind it. The Helepolis bore a fearsome complement of heavy armaments, with two 180-pound catapults, and one 60-pounder on the first floor, three 60-pounders on the second, and two 30-pounders on each of the next five floors. Apertures, shielded by mechanically adjustable shutters, lined with skins stuffed with wool and seaweed to render them fireproof, perforated the forward wall of the tower for firing the missile weapons. On each of the top two floors, soldiers could use two light dart throwers to easily clear the walls of defenders.
Siege of Rhodes
As the Helepolis was pushed towards the city, the Rhodians managed to dislodge some of the metal plates, and Demetrius ordered it withdrawn from battle to protect it from being burned. Following the failure of the siege, the Helepolis along with the other siege engines were abandoned, and the people of Rhodes melted down their metal plating and sold abandoned weapons, using the materials and money to build a statue of their patron god, Helios, the Colossus of Rhodes, known as one of the ancient Seven Wonders of the World. Vitruvius offers an alternative version, in which the Rhodians begged Diognetus, once the town architect of Rhodes, to find a way to capture the Helepolis. By cover of night he had the Rhodians knock a hole through the wall and channel large amounts of water, mud and sewage onto the area where the Helepolis was expected to attack the following day. Diognetus was successful; the tower was brought forth to the anticipated attack position and became irretrievably stuck in the mire. Once the siege was lifted, the Rhodians sold Demetrius' abandoned engines and used the money to erect the enormous Colossus of Rhodes.
