Arx (Roman)

At Rome, sentries were traditionally posted on the Arx to watch for signals displayed on the Janiculan Hill if an enemy approached.

During the regal period, some members of the elite were permitted to live on the Arx, among them the legendary Sabine leader Titus Tatius.

The house of Marcus Manlius Capitolinus, a patrician champion of the plebs who was convicted of seeking kingship, was torn down at this time and later became the site of the Temple of Juno Moneta.

On the Arx was located the auguraculum, the open space where the augurs conducted the rituals that determined whether the gods approved of whatever undertaking was at hand, public business or military action.

In Lavinium, south of Rome, Castello Borghese is thought to be the possible site of the Roman-era arx constructed in the port city.