Most sword-and-sandal epics of the 1950s and 1960s were set in either classical Greece or even earlier (Hercules, Ulysses, The Giant of Marathon) or the later Roman period (Ben Hur, The Magnificent Gladiator, Quo Vadis).

Rhodes has just finished constructing an enormous colossal statue of the god Apollo to guard its harbor and is planning an alliance with Phoenicia, which would be hostile to Greece.

The rebels learn of this plan and decide to apply to the Greeks for help; Darios, who is forbidden to leave Rhodes as he is suspected of being a spy, is to serve as an unwitting message carrier.

Diala, who longs for power, betrays Darios and has Thar have the rebels nearly wiped out – with the exceptions of Mirte and Koros, Peliocles' sister and brother, who have hidden.

Peliocles and his men are captured and forced to provide amusement in the local arena; but just when Darios arrives to publicly expose the traitor's plot, Thar executes his coup and kills Serse and his retainers.

The rebels immediately set out to carry out their plan, but the rebellion seems doomed to fail: Darios is captured while he tries to work the release mechanism to the dungeons, and Koros, who accompanies him, is killed.

[6] Leone filmed exterior scenes at the Laredo harbour, Cantabria, the Bay of Biscay, the Manzanares el Real and Ciudad Encantada at Cuenca.

[17] Although no physical references of the original Helios Colossus are known to exist, the structure is rendered in this film as being an Etruscan image of the god Apollo following the kouros style of sculpture, with a slight “archaic smile.” It is about 300 feet high (nearly three times the height of its historical counterpart) and holds a bowl at chest level with elbows raised outward, straddling the harbor entrance.