Commodus, the Roman emperor who inspired the film Gladiator, may have had a private arena where he killed wild animals and practised his warrior moves in front of hundreds of people.

Archaeologists from New Jersey's Montclair State University have discovered an amphitheatre-like structure which they believe once belonged to the emperor, who was famous for his feats as a gladiator and apeing the combatants who fought in front of huge crowds in ancient Rome.

The archaeological site is located about 18 miles (28km) from Rome in the ancient Via Appia region of the modern Italian territory of Genzano.

The New Jersey team have been excavating the remains of the complex since 2010. They claim ancient textual references and the discovery of some high-quality marble busts at the site in the 18th century suggest the villa belonged to the Antonine imperial family, which included emperors Antoninus Pius (ruled 138-161 CE), Marcus Aurelius (ruled 161-180 CE), and Commodus (ruled 180-192 CE).

The newly-excavated arena, described as a miniature of the Colosseum in Rome, was found near a bathing complex. It spans more than 9000 sq m and had a capacity of over 1300 seats plus an imperial stage. Archaeologists believe that Commodus used the amphitheatre to kill animals, Italian daily Il Messaggero reports.

"These investigations have brought to light hundreds of fragments of imported marble floor and wall decoration, evidence for lavish, colored glass mosaics, and an elliptical, amphitheatre-like structure that may be connected with Commodus's interests in performing in the arena," Deborah Chatr Aryamontri, co-director of the excavation, said.

A spiral staircase that descends almost three metres to underground chambers below the mini-Colosseum suggests Commodus may have had his own private dressing area where he prepared to kill the wild beasts, Aryamontri concluded.

Archaeologists also say that the arena might have also been used for the performances of naval battles.

It is claimed that Commodus, who was obsessed with being a gladiator, featured over 735 times in bouts during his lifetime - even though he was a weak and cruel ruler who would regularly inflict barbaric punishments on innocent people.

He ordered his subjects to regard him as the second coming of Hercules, because of his ability to kill wild animals.

In the 2000 movie Gladiator, which won five Oscars, Commodus, played by Joaquin Phoenix, abandons his imperial throne to take on army commander Maximus, played by Russell Crowe.