Invented by the Greek engineer Polyidus of Thessaly, the Helepolis or 'city-taker' was the biggest siege engine ever constructed. King Demetrius I of Macedon commissioned the architect Epimachus of Athens to build the biggest recorded Helepolis, which he used in the failed siege of Rhodes in 305BC. This huge construction was said to be nearly forty metres tall, split into nine storeys, with catapults at its base and two stairways giving access to its multiple levels. Built entirely of wood, it was covered with iron plates to protect it from fire. During the siege the Rhodians managed to dislodge some of these plates, prompting Demetrius to withdraw the weapon for fear of its destruction.
