In 270 AD, Emperor Aurelian realized that the threat of Germanic tribes was too high, as they were near the borders of the Roman empire, so in 271 AD, he began planning for a defensive wall that would surround Rome and protect it from invaders. The previous wall, the Republican Wall, was built at the end of the fourth century, which replaced an even older wall. Originally, the Aurelian wall was nineteen kilometers long, and around six to eight meters high. The walls were three and a half meters thick, and the wall had a squared tower at every thirty meters, roughly four hundred towers in total around the entire wall. Eighteen entrances were grand gates, for example the Porta Latina, and Porta San Sebastiano, which were protected by other towers. The wall was completed by Probus, the emperor after Aurelian, finished the construction as projeced, but it took the barbarians one century to reach the city. Even after the wall was completed, Emperors Maxentius and Honorius made additions between the end of the fourth century and the beginning of the fifth century. However, this wasn’t enough to stop the barbarians, and the city was raided by Visigoths in the year 410.

       The Aurelian wall added monuments and buildings along the wall, building the wall to intersect these other structures, saving time and resources. Buildings like the Castel Sant’angelo (Hadrian’s Mausoleum) Amphitheatrum Castrense, a Roman amphitheater built out of brick in the third century, the Pyramid of Cestius, an Egyptian styled pyramid built in 12 BC, and a portion of the Aqua Claudia aqueduct, which supplied the Roman districts with water. Two thirds of the wall still stand and are intact today, in very good shape.