During the short reign of Aurelian (270 – 275 AD), the Roman Emperor waged battle against many enemies such as the Goths, Vandals and Gallic Empire. His victories consolidated the Empire’s provinces in the east and west. Fearing retaliatory attacks by barbarians, he ordered a massive wall around the city. The first iteration was finished during the reign of Emperor Probus (276 – 282). The initial brick and cement curtainwall stretched for 12 miles, was 26 feet high and protected by a guard tower every 100 feet. This encircled about 3,500 acres of Rome. The defense was extended through the early 5th century. Surprisingly, more than 60% of the walls and gates are still standing.