Arx is the Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 word for citadel

Citadel

A citadel is a fortress for protecting a town, sometimes incorporating a castle. The term derives from the same Latin root as the word "city", civis, meaning citizen....

. In the ancient city of Rome

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

, the Arx, not always capitalized, was located on the northern spur of the Capitoline Hill

Capitoline Hill

The Capitoline Hill , between the Forum and the Campus Martius, is one of the seven hills of Rome. It was the citadel of the earliest Romans. By the 16th century, Capitolinus had become Capitolino in Italian, with the alternative Campidoglio stemming from Capitolium. The English word capitol...

, and is sometimes specified as the Arx Capitolina. Sentries were posted there to watch for a signal to be displayed on the Janiculum

Janiculum

The Janiculum is a hill in western Rome, Italy. Although the second-tallest hill in the contemporary city of Rome, the Janiculum does not figure among the proverbial Seven Hills of Rome, being west of the Tiber and outside the boundaries of the ancient city.-Sights:The Janiculum is one of the...

 if an enemy approached. A red flag would be raised on the Arx and a trumpet blown. It was not regularly garrisoned, however, and should not be regarded as a "fort." However, in the Gallic siege of Rome

Battle of the Allia

The Battle of the Allia was a battle of the first Gallic invasion of Rome. The battle was fought near the Allia river: the defeat of the Roman army opened the route for the Gauls to sack Rome. It was fought in 390/387 BC.-Background:...

, the Arx was considered the point of last retreat, the capture of which was synonymous with the capture of the city. It thus held a symbolic power beyond its importance in military strategy, and was a central place in archaic Roman religion

Religion in ancient Rome

Religion in ancient Rome encompassed the religious beliefs and cult practices regarded by the Romans as indigenous and central to their identity as a people, as well as the various and many cults imported from other peoples brought under Roman rule. Romans thus offered cult to innumerable deities...

.

On the Arx was located the auguraculum, the open space where the augur

Augur

The augur was a priest and official in the classical world, especially ancient Rome and Etruria. His main role was to interpret the will of the gods by studying the flight of birds: whether they are flying in groups/alone, what noises they make as they fly, direction of flight and what kind of...

s conducted the rituals that determined whether the gods approved of whatever undertaking was at hand, public business or military action. Major temples

Roman temple

Ancient Roman temples are among the most visible archaeological remains of Roman culture, and are a significant source for Roman architecture. Their construction and maintenance was a major part of ancient Roman religion. The main room housed the cult image of the deity to whom the temple was...

 on the Arx include that of Juno Moneta (established 344 BC), where the mint was located; Concordia

Concordia (mythology)

In Roman religion, Concord was the goddess of agreement, understanding, and marital harmony. Her Greek version is Harmonia, and the Harmonians and some Discordians equate her with Aneris. Her opposite is Discordia ....

 (217 BC); Honor

Honos

In Roman mythology, Honos was the god of chivalry, honor and military justice. He was depicted in art with a lance and a cornucopia. He was sometimes identified with the deity Virtus....

 and Virtue; and Vediovis. Jupiter

Jupiter (mythology)

In ancient Roman religion and myth, Jupiter or Jove is the king of the gods, and the god of the sky and thunder. He is the equivalent of Zeus in the Greek pantheon....

, however, was the god of the Arx.

In the early Republic, patricians might live on the Arx, among them Titus Tatius

Titus Tatius

The traditions of ancient Rome held that Titus Tatius was the Sabine king of Cures, who, after the rape of the Sabine women, attacked Rome and captured the Capitol with the treachery of Tarpeia. The Sabine women, however, convinced Tatius and the Roman king, Romulus, to reconcile and subsequently...

. After 384 BC, the senate

Roman Senate

The Senate of the Roman Republic was a political institution in the ancient Roman Republic, however, it was not an elected body, but one whose members were appointed by the consuls, and later by the censors. After a magistrate served his term in office, it usually was followed with automatic...

 banned patrician dwellings from the Arx and Capitolium. The house of Marcus Manlius Capitolinus, a patrician champion of the plebs

Plebs

The plebs was the general body of free land-owning Roman citizens in Ancient Rome. They were distinct from the higher order of the patricians. A member of the plebs was known as a plebeian...

, was torn down, and became the site of the temple of Juno Moneta.

The Romans also referred to the citadel of other cities as an arx.