The series takes place over more than 20 years, but some of the characters don't age over that time.
In real life, Servilia died after Atia.
Several historical changes were made to move the story along. Octavian was in Illyria undergoing military training when Caesar was killed. Livia was Octavian's third wife. When she married him, she had two sons, Drusus and Tiberius. Drusus was married to Antonia, daughter of Marc Antony and Octavia, and was the grandfather of Caligula and father of Claudius. Octavian had one natural child, Julia, by his first wife. Julia was married to Tiberius.
Slaves at auction wear loin cloths. Young women, and slaves being sold as laborers, were displayed naked.
The cast says Domina and Dominus frequently. They're used in the vocative; the masculine form would be Domine.
The series implies that the break between Caesar and Pompey happened after the death of Julia, Caesar's daughter and Pompey's wife. Julia had been dead for several years when Caesar's conflict with Rome started.
In the series, Octavian's mother, Atia, is alive in 31 BC. She died in 43 BC.
In one scene, a character is suddenly awoken. He yells out "Oh, Jesus!".
This is taking place decades before Jesus's time.
In the series, candles are the primary source of lighting. Romans mostly used oil lamps.
In the close-up views of sandals, especially the legionaries' sandals, a modern rubber sole is visible. Shoes of the period had leather soles.
Captive birds are shown frequently, including Macaws and Amazon parrots from America, and cockatoos from Australia. Those continents were unknown to the Romans; they wouldn't have traveled to obtain the birds.
According to the DVD commentary, the creators included camels in scenes set in Egypt to make them look exotic compared to Rome. Camels were useless in ancient Alexandria. It was built on a marshy island in the Nile delta, and it's very hard for camels to walk over soft, humid soil.
In the series, Cato is much older than Cicero and Pompey. He was actually more than 10 years younger.