The Castra Praetoria (English: Praetorian Barracks) was a fortified military barracks in Rome, incorporated into the north-eastern edge of the city walls. It was originally constructed to house the Praetorian Guard, the official bodyguards of the Roman Emperors.
The Castra were erected just outside Rome by order of the Praetorian Prefect Sejanus, between 20 and 23 AD, during Emperor Tiberius' reign, to house the nine cohorts of the Praetorian Guard, the influential Imperial guard. When Emperor Aurelian encircled the city with walls, he had the barracks incorporated in the fortification.
After Constantine's victory over Maxentius in 312, he disbanded the Guard and destroyed the barracks, as Praetorians had been fighting on Maxentius' side.
Following the kidnapping of Bartolomeo d'Alviano's wife, Pantasilea Baglioni, the fortress was infiltrated by Ezio Auditore da Firenze and a contingent of Bartolomeo's mercenaries disguised as French soldiers. Octavian was killed in the surprise attack, and his forces abandoned the fortress not long after.