Neil Marshall and his director of photography Sam McCurdy spent about two years discussing the look of the film before making it. One thing they were adamant about was that it should be shot on location and nowhere near a green screen.
The Picts in the film are speaking Scots Gaelic. No written record of the Pictish language exists, but historians believe the modern language most similar to theirs is Welsh. However, director Neil Marshall thought viewers would be confused by a tribe in Scotland speaking Welsh.
German archaeologists have found evidence of the 9th Legion on the banks of the Rhine River and carbon-dated them long after these events took place, suggesting that rather than being wiped out, the reason that there is no evidence of the 9th Legion being in Scotland after these battles is that they moved to Germany.
The Eagle (2011) can almost be seen as a sequel to this film, as it picks up the same storyline about the 9th Legion some 23 years later when the general's son comes back to find the truth about the Legion's disappearance and to collect the Eagle Standard.
Centurion's depiction of the massacre of the Roman Ninth Legion is modelled on the historical Battle of the Teutoburg Forest in 9AD, in which a German mercenary supposedly loyal to Rome led three legions of Publius Quinctilius Varus along a narrow pathway in the German forest, where terrain blocked their escape and they were ambushed by Germans under the leadership of Arminius. Roman losses were 15-20,000 men.