Ancient Rome's Castra Praetoria

The Castra Praetoria was the fortified military camp of the Praetorian Guard, who were the elite force charged with protecting the Emperor of Rome. The Castra stood for nearly 300 years as the physical manifestation of the Guard’s strength.

It originated in 23 CE during the reign of Emperor Tiberius, who was persuaded by Sejanus, Prefect of the Praetorian Guard, that the Guard’s cohorts should have a central base from which to respond rapidly to any sudden emergency.

The Castra was situated on high ground just outside the city walls. It had the pattern of a regular military camp but was permanent, being composed of pink and red brickwork. Later enhancements included improvements to the living quarters and heightening of the external walls.

Notable events that took place at the Castra Praetoria included:

• In 41 CE, after the assassination of Emperor Caligula, his uncle Claudius spent several days there while the Guard debated his fate and finally agreed to make him the next Emperor.
• In 54 CE, Claudius was poisoned by his wife Agrippina, with the possible assistance of Burrus, the Prefect of the Guard. This was done so that her son Nero could became Emperor, in preference to Britannicus, who was Claudius’s son by a previous marriage. Burrus was able to prove his loyalty to Agrippina by taking Nero to the Castra and gaining the approval of the Guard.
• In 69 CE Emperor Galba was assassinated and his head was carried around the Castra on a spear while the next Emperor, Otho, was declared his successor.

However, Otho’s reign was a short one and he was killed in battle against the forces of Vitellius. The Praetorian Guard were split between those loyal to Otho and to Vitellius. A siege of the Castra took place and much of it was destroyed.

• In 193, after the murder of Pertinax, an extraordinary event took place when rival candidates for the imperial throne held what was virtually an auction for the job. The Praetorian Guard, which had become lazy and self-indulgent under Pertinax’s predecessor, Commodus, made it clear that their approval would go to the man who promised them the highest pay. The candidates, Sulpicianus and Didius Julianus, both went to the Castra and stood either side of the external wall. They then shouted their bids across the wall until Sulpicianus was forced to concede to the wealthier man.

This charade so annoyed the citizens of Rome that they laid siege to the Castra, the walls of which proved to be too strong. Hundreds died in the fighting that followed.

When a second siege failed, the citizens cut off the Castra’s water supply, after which the Praetorians charged out of the Castra and created mayhem in the city with a great deal of burning and looting, leaving much of the metropolis in ruin and chaos.

The Castra Praetoria survived until 312, after Constantine’s victory at the Battle of the Milvian Bridge. He marched on Rome, rode to the Castra and decreed its destruction. The walls were torn down brick by brick, with hardly anything left for later archaeologists to explore.