A wall commissioned by Aurelian, the 30th Emperor of Rome, in 271 A.D. The wall was deemed necessary, as the old wall, the Republican or Servian Wall, built by Servius Tullius, was in ruin, and no longer surrounded the city in its entirety. The threat of a barbarian army overrunning Rome did not sit well with the Emperor, so he endeavored to build an impedance strong enough to stop any crowd of invaders.

The wall was completed in 275 A.D.; several months after Aurelian had been assassinated by his officers. Upon completion the new wall ran for more than twelve miles around Rome. It was 60 feet high and built of brick-faced concrete. Large square towers were created every 100 roman feet, the equivalent of about 30 meters.

In 401 A.D. the danger of invasion by the powerful Gothic army induced Emperor Honorius to strengthen the walls. The height was doubled, the towers were raised and the gates made smaller. Walkways were covered and arrow loops were opened, while above a further walk was built and protected by merlons and crenels. At the major roads, like the via Latina, huge arched gates with twin semi-circular towers were built. Several, such as the aforementioned Porta Latina, and the Porta Asinaria, still exist today.

The wall's height was later increased by emperor Maxentius in the early 5th century, and further updated and repaired by the Byzantine general Belisarius in the 6th century.

The Aurelian wall is an excellent example of the typical Roman brick technique of the time. It was constructed of "green brick" with a concrete center. Roman green brick was flatter, longer, wider than modern-day bricks, and, since they were not kiln-fired, tended to be softer.