In an interview with Simon Mayo, Sir Ridley Scott said that he sold the Kingdom of Heaven (2005) set to the Moroccan government for $10 because it was cheaper than dismantling it. He then had to hire it from the same government for use in this movie.
The rhinoceros fight was originally meant to be in Gladiator (2000). It was changed because the special effects of the time couldn't convincingly recreate them and real rhinos are impossible to tame.
In the years following the release of the first film, there were numerous attempts to write a sequel. One idea suggested by producer Douglas Wick was to have Maximus' body be placed in a cave, and be resurrected similar to Jesus, but Russell Crowe told him "I don't think we have the rights to that story." Musician Nick Cave was also invited to draft a version by Crowe and Sir Ridley Scott. His version focused on the more mythical elements of Ancient Rome, and would have seen Maximus arrive in the afterlife, only to be faced with other souls who are yet to ascend further. He is eventually tasked by Jupiter and other Roman deities to return to earth to find and kill Hephaestus, a former deity who has betrayed them. From there, he is resurrected as a Christian and finds himself journeying back to Rome, on a mission to stop Christianity from spreading, while crossing paths with the new Emperor, Lucius. The movie would have ended with Maximus being cursed to live for an eternity, featuring a montage of the soldier battling through the Crusades, World War II, and the Vietnam War, eventually revealing a modern-day Maximus working at the Pentagon in Washington. The studio decided not to go through with this version, but the script is available to read online.
Following the first battle, Acacius says "Vae victis" which is Latin for "Woe to the defeated".
The lines "The gates of hell are open night and day; / Smooth the descent, and easy is the way: / But to return, and view the cheerful skies, / In this the task and mighty labor lies." are from the English poet John Dryden's 1697 translation of Vergil's epic poem Aeneid. The warning comes from the Cumaean Sybil as Aeneas prepares to descend to the underworld to see the shade of his father, Anchises. As Vergil imagines it, Aeneas' travels culminate in the founding of Rome.