Located deep in the heart of the Imperium Romanum, the Castra Italia (English: Italian Fortress) is the military headquarters of the Legion. The facility was carved into a mountain north of the Italian city of Mediolanum. With its barracks situated 1.8 km from the mountain surface, the base can continue to operate under the heaviest bombardment. Caesar Raphael referred to the complex after its original completion in 1981 as the "most secure of Rome's holdings since the spade of Romulus first touched earth." In some ways, his words underscore the level of security employed in maintaining this military base.
The City of Rome has barely suffered the threat of war since Attila, the Great Scourge, was killed at the walls of Mediolanum. There has been little need to build intrinsically secure fortresses for the national military command since distance from the limites alone suffices to keep its personnel safe. Nevertheless, the always paranoid emperors have built incredible defensive structures in Italy to prepare for the worst or protect important personnel from a possible rebellion. Rome itself has received the gift of a succession of defensive walls from the original Servian Walls to the early modern Caesarian Walls. Its original defensive structure was the famous Arx Capitolina inside the city built by Romulus. This has long since been superseded by other urban citadels.
Once Caesar Draco secured a new border for Europe in Magna Germania, the necessity of defending Italy subsided. Despite the invasion of the Imperium from the east by the Golden Horde of Mongolia during the Bellum Mundum, the Senate and Caesar saw no need for constructing better defensives as far into Europe as Italy or even Noricum. It was Caesar Raphael who believed that the increasing spread of nuclear weapons threatened even the core provinces of the empire. As a symbol of the defence of Rome and as a strategic location, the Alpine mountains near Mediolanum were considered a prime site for a secure base.
Boring deep into the mountain was a serious engineering challenge. Billions of denarii were funneled into the excavation and construction that followed. However, its cost pales in comparison with the ongoing colonization of Mars and launch of weapons satellites, as well as requiring only a fraction of the tens of billions of denarii spent each year on the military.