''Arx'' is a

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word meaning "

citadel A citadel is the most fortified area of a town or city. It may be a castle, fortress, or fortified center. The term is a diminutive of ''city'', meaning "little city", because it is a smaller part of the city of which it is the defensive core. ...

". In the ancient city of Rome, the ''arx'' was located on the northern spur of the Capitoline Hill, and is sometimes specified as the ''Arx Capitolina''.

History

At Rome, sentries were traditionally posted on the ''Arx'' to watch for signals displayed on the Janiculan Hill if an enemy approached. A red flag would be raised and a trumpet blown. The ''Arx'' was not regularly garrisoned, however, and should not be regarded as a "fort." However, in the Gallic siege of Rome (387 BC), the ''Arx'' was considered the point of last retreat, the capture of which was synonymous with the capture of the city. It held a symbolic power beyond its importance in military strategy, and was a central place in archaic Roman religion. During the regal period, some members of the elite were permitted to live on the ''Arx'', among them the legendary Sabine leader Titus Tatius. After 384 BC, the

Senate A senate is a deliberative assembly, often the upper house or chamber of a bicameral legislature. The name comes from the ancient Roman Senate (Latin: ''Senatus''), so-called as an assembly of the senior (Latin: ''senex'' meaning "the el ...

banned all private dwellings from the Capitoline Hill, including the ''Arx.'' The house of Marcus Manlius Capitolinus, a patrician champion of the ''

plebs In ancient Rome, the plebeians or plebs were the general body of free Roman citizens who were not patricians, as determined by the census, or in other words "commoners". Both classes were hereditary. Etymology The precise origins of the gro ...

'' who was convicted of seeking kingship, was torn down at this time and later became the site of the

Temple of Juno Moneta The Temple of Juno Moneta (Latin: Templum Iunonis Monetæ) was an ancient Roman Kingdom, Roman temple that stood on the Arx (Roman), Arx or the citadel on the Capitoline Hill overlooking the Roman Forum. Located at the center of the city of Rome, ...

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

augur An augur was a priest and official in the ancient Rome, classical Roman world. His main role was the practice of augury, the interpretation of the will of the List of Roman deities, gods by studying events he observed within a predetermined s ...

s conducted the rituals that determined whether the gods approved of whatever undertaking was at hand, public business or military action. This auguraculum was the stone where the elected monarch, during the

Roman Kingdom The Roman Kingdom, also known as the Roman monarchy and the regal period of ancient Rome, was the earliest period of Ancient Rome, Roman history when the city and its territory were King of Rome, ruled by kings. According to tradition, the Roma ...

, was seated by the augurs with his face to the south. Major temples on the ''Arx'' include that of Juno Moneta (established 344 BC), where the mint was located; Concordia (217 BC);

Honor Honour ( Commonwealth English) or honor (American English; see spelling differences) is a quality of a person that is of both social teaching and personal ethos, that manifests itself as a code of conduct, and has various elements such as val ...

and

Virtue A virtue () is a trait of excellence, including traits that may be morality, moral, social, or intellectual. The cultivation and refinement of virtue is held to be the "good of humanity" and thus is Value (ethics), valued as an Telos, end purpos ...

; and Vediovis.

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

, however, was the god of the ''Arx''. Jerzy Linderski, "The Augural Law", ''Aufstieg und Niedergang der römischen Welt'' II.16 (1986), p. 2226, note 312, and 2291.

Other ''arces''

The Romans also referred to the citadel of other cities as an ''arx'' (plural ''arces''). Excavations in Cosa,

Tuscany Tuscany ( ; ) is a Regions of Italy, region in central Italy with an area of about and a population of 3,660,834 inhabitants as of 2025. The capital city is Florence. Tuscany is known for its landscapes, history, artistic legacy, and its in ...

, conducted in 1948–54 and 1965–72, uncovered the settlement's ''arx''. Frank E. Brown and his team studied the site extensively when they began the Cosa excavations in 1948. The citadel was a fortified hill on which were built several temples, including the so-called "capitolium" of Cosa. In

Lavinium Lavinium was a port city of Latium, to the south of Rome, midway between the Tiber river at Ostia Antica, Ostia and Antium. The coastline then, as now, was a long strip of beach. Lavinium was on a hill at the southernmost edge of the ''Silva La ...

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

Londinium Londinium, also known as Roman London, was the capital of Roman Britain during most of the period of Roman rule. Most twenty-first century historians think that it was originally a settlement established shortly after the Roman conquest of Brit ...

was located in the northwest corner of the present-day

City of London The City of London, also known as ''the City'', is a Ceremonial counties of England, ceremonial county and Districts of England, local government district with City status in the United Kingdom, city status in England. It is the Old town, his ...

, south of

Cripplegate Cripplegate was a city gate, gate in the London Wall which once enclosed the City of London, England. The Cripplegate gate lent its name to the Cripplegate Wards of the City of London, ward of the City, which encompasses the area where the gat ...

. It was constructed around 120 and dismantled around the time of

Diocletian Diocletian ( ; ; ; 242/245 – 311/312), nicknamed Jovius, was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia (Roman province), Dalmatia. As with other Illyri ...

References

* Unless otherwise noted, general background and references to ancient sources from Samuel Ball Platner and Thomas Ashby, "Arx," ''A Topographical Dictionary of Ancient Rome'' (Oxford University Press, 1929), LacusCurtiusbr>edition.
Topography of the ancient city of Rome Roman citadels in Italy {{Rome landmarks