Epimachus of Athens

Assuming the figures recorded in the writings of several ancient historians, including Diocleides of Abdera, Vitruvius and Plutarch are accurate, the Helepolis was and remains the largest siege machine ever erected; it was a colossal, tapered, tower-like structure 60 feet (20 metres approx.)

All exposed sides of the helepolis were rigidly defended; iron plates protected the wooden structure from possible inflammation, and additional defences, such as great stretches of hide plastered on the interior, were placed to withstand the power of ballista and catapult assault.

The inside of the machine was divided into nine separate stories, each accessible through a long flight of stairs that wound from the ground floor to the very top.

[6] Despite the seemingly indestructible design of the Helepolis, many of the iron plates were dislodged during the siege, rendering the great machine highly vulnerable.

Fearing that the laboriously constructed Helepolis would fall victim to the intense fire that was directed towards it, Demetrius I of Macedon ordered that it be withdrawn from the war field to prevent any further damage.