Blooper

While training for the third day of gladiatorial games, the overseer makes Lucius pull the oar machine by himself. Lucuis badly blisters the palms of his hands. During the gladiatorial "sea battle" the next day, Lucuis's hands have no blisters.

Lucius gets marked by a hot branding iron once he is captured. That mark frequently appears and disappears towards the end of the movie.

After Lucius bites the monkey, his mouth and chin are covered in blood. It disappears shortly afterward, without any time for washing.

When Ravi is healing Lucius after a fight, there is no blood on Lucius' face. When Ravi asks him to go to where they bury rebel gladiators, a whole side of Lucius' face is covered in blood.

When Lucius enters the arena 2 hours and 6 minutes into the film, his armour has the angel on his right side and Maximius' wife and son on his left. This is obvious reverse film as they are the other way round for the rest of the movie.

The naval battle is described as "the reenactment of the Battle of Salamis between the Persians and the Trojans." The battle was between the Persians, Sparta, and Athens.

In the beginning of the film, when Lucius is tending to his field in Numidia, pumpkins are growing. At the time, pumpkins grew only in the Americas.

The Praetorian guard and the main legion of the Emperors are clad in purple, and have purple banners. Purple dye was so expensive in Ancient Rome that even Emperor Nero decreed it for his own personal use, and issued the death penalty for anyone who dared to wear purple.

Caracalla was assassinated by a soldier named Julius Martialis during a military campaign against the Parthians. Martialis, who was part of his guard, killed him while Caracalla was relieving himself at a stopover in the imperial caravan. The assassination is said to have been instigated by the Praetorian prefect Macrinus, who had reason to fear for his life after disagreements with Caracalla.

Sharks are difficult to transport and keep in captivity, even in modern times. There is no practical way Ancient Romans could have brought sharks into the Colosseum.

The Roman god of the sea was Neptune, not Poseidon. However, educated Romans spoke and wrote in Greek routinely, and calling gods by their Greek names was a common affectation.

Lucilla and Lucius are called the queen and prince of Rome. The Roman monarchy had been eliminated about 700 years earlier. Calling Lucilla a "queen" could be a way to criticize her as a tyrant who wanted to reinstate the monarchy. "Prince" meant "principal citizen," i.e. emperor, a title to which Lucius had claim.

Lucius Verus is pitted against a rival fighter standing on top of a rhinoceros, its horns covered in blood. Gladiators only fought men. Bestiarii, who fought animals, were a separate category of combatants. However, it is clear that these emperors do not adhere to the standard rules of gladiator combat.

English sentences are engraved in the walls of the Colosseum and other Roman buildings. It's a convenience for modern audiences, routine in period dramas.

When sparring with Lucius, Viggo is wearing a spiked cestus on each hand and hit Lucius several times, but Lucius doesn't get a scratch on his face or body. The spikes were obviously sharp and made to wound.

Men and women are incorrectly shown seated together in the Colosseum. Seating was strictly segregated by class and gender. The seating chart of the Colosseum has elite men in the front, free men in the middle section, with slaves and women (regardless of social class) at the very back.

Naval battles were only staged in the first year after the Colosseum was built. After the construction of the Hypogeum it was no longer possible to flood the arena.

A man sitting a cafe reads a newspaper. Mass-produced paper didn't exist at the time. "Acta Diurna," government announcement bulletins, were carved in metal or stone and posted in public places.

Trebuchets are used for city defense. The trebuchet was developed in China in the fourth century BCE, but it didn't reach the Middle East until the sixth and seventh century CE. The counterweight-driven trebuchets shown in the film were developed in Europe in the 1100s.

Emperor Caracalla demands that General Acacius conquer Persia. By the time the movie is set, the region was called Parthia.

The Romans emphasize invading Numidia. By the time of Geta and Caracalla's rule, North Africa had been Roman provinces for over 150 years. The real siege of Numidia took place during the Jugurthine War, between 112 BCE and 106 BCE, almost three centuries before the film takes place.

On numerous occasions a sword is either picked up from the dirt or swung in the air without making contact, but it makes the sound of a sword being unsheathed.

Coming from the port of Ostia, it would not be necessary to cross a river to enter Rome.

The Colosseum appears to be on a hill and towers high above Rome. In fact, it sits on the floor of a low valley between the city's Caelian, Esquiline and Palatine Hills.

When the captured Numidians are taken to be trained near Rome, the landscape is clearly North Africa.