The Aurelian Wall was not the first protective wall around Rome, that honor goes to the Servian Wall, but it is clearly the best preserved. Whereas of the Servia Wall but little remains, the many surviving stretches of the Aurelian Wall are still considered to form the historical center of the city.
Aurelian Wall Rome
History and description
The first defensive wall around Rome was built in the early 4th century BC. In the centuries following its construction, Rome gradually became ever more important. As a result, the need for a wall diminished and the Servian Wall was left to decay.
It was not until the 3rd century AD that the Roman Empire again felt the need to build a protective wall around the city. Until then, the Pax Romana (“Roman Peace”) had ensured that no one could or would attack Rome.
Of course, the vast expanse of the Empire also had something to do with this. Before would-be conquerors managed to come even near Rome, they had already been ambushed somewhere else or simply been defeated on the battlefield.
The Aurelian Walls were built by Emperor Aurelius and lasted for two centuries. After the fall of the Empire, the Barbarians destroyed big parts of the wall.
Sometimes it takes a while to realize that you are looking at a part of the Aurelian Walls. In several places more recent constructions have been integrated into them. A good example is formed by the walls on either side of the Porta del Popolo.
It also often happened that parts of the Aurelian Wall were used for the aqueducts providing the city with water. The best examples for this can be seen in the area around Porta Maggiore.
The Muro Torto (which from the 15th to the 17th century was also called Muro Malo) that borders the Villa Borghese is a wall from Republican times, which was later integrated into the Mura Aureliane. The wall was called Malo because prostitutes, thieves, and anythone else the pope did not like, used to be buried there.