Rubicon in Northeastern Italy

The Rubicon (Latin: Rubico, Italian: Rubicone) is a shallow river in northeastern Italy, about 80 kilometres long, running from the Apennine Mountains to the Adriatic Sea through the southern Emilia-Romagna region, between the towns of Rimini and Cesena. The Latin word rubico comes from the adjective "rubeus", meaning "red". The river was so named because its waters are colored red by mud deposits. It was key to protecting Rome from Civil War.

The idiom "Crossing the Rubicon" means to pass a point of no return, and refers to Julius Caesar's army's  crossing of the river in 49 BC, which was considered an act of insurrection. Because the course of the river
has changed much since then, it is impossible to confirm exactly where the Rubicon flowed when Caesar and his legions crossed it, even if most evidence is linking it to the river officially so named. The river is perhaps most known as the place where Julius Caesar uttered the famous phrase "alea iacta est" - the die is cast.

History

During the Roman republic, the river Rubicon marked the boundary between the Roman province of  Cisalpine Gaul to the north-east and Italy proper (controlled directly by Rome and its socii (allies)) to the
south. On the north-western side, the border was marked by the river Arno, a much wider and more important waterway, which flows westward from the Apennine Mountains (its source is not far from Rubicon's source) into the Tyrrhenian Sea. Governors of Roman provinces were appointed promagistrates with imperium (roughly, "right to command") in their province(s). The governor would then serve as the general of the Roman army within the territory of his province(s). Roman law specified that only the elected magistrates (consuls and praetors) could hold imperium within Italy. Any promagistrate who entered Italy at the head of his troops forfeited his imperium and was therefore no longer legally allowed to command troops.

Exercising imperium when forbidden by the law was a capital offence, punishable by death. Furthermore, obeying the commands of a general who did not legally possess imperium was also a capital offence. If a general entered Italy whilst exercising command of an army, both the general and his soldiers became outlaws and were automatically condemned to death. Generals were thus obliged to disband their armies before entering Italy. In 49 BC, supposedly on January 10 of the Roman calendar, G. Julius Caesar led one legion, the Legio XIII Gemina, south over the Rubicon from Cisalpine Gaul to Italy to make his way to Rome. In doing so, he (deliberately) broke the law on imperium and made armed conflict inevitable. According to the historian Suetonius, Caesar uttered the famous phrase ālea iacta est ("the die has been cast").[1] Caesar's decision for swift action forced Pompey, the lawful consuls (G. Claudius Marcellus and L. Cornelius Lentulus Crus), and a large part of the Roman Senate to flee Rome in fear. Caesar's subsequent victory in Caesar's civil war ensured that punishment for the infraction would never be rendered. Suetonius's account depicts Caesar as undecided as he approached the river, and attributes the crossing to a supernatural apparition. The phrase "crossing the Rubicon" has survived to refer to any individual or group committing itself irrevocably to a risky or revolutionary course of action, similar to the modern phrase  "passing the point of no return".

Location confusion and resolution

After Caesar's crossing, the Rubicon was a geographical feature of note until Emperor Augustus abolished the Province of Gallia Cisalpina (today’s northern Italy) and the river ceased to be the extreme border line of Italy. The decision robbed the Rubicon of its importance, and the name gradually disappeared from the local toponymy.

After the fall of the Roman Empire, and during the first centuries of the Middle Ages, the coastal plain between Ravenna and Rimini was flooded many times. The Rubicon, as with other small rivers of the region, often changed its course during this period. For this reason, and to supply fields with water after the revival of agriculture in the late Middle Ages, during the 14th and 15th centuries, hydraulic works were built to prevent other floods and to regulate streams. As a result of this work, these rivers eventually started flowing in straight courses, as they do today.

With the revival of interest in the topography of ancient Roman Italy during the 15th century, the matter of
identifying the Rubicon in the contemporary landscape became a topic of debate among Renaissance humanists.To support the claim of the Pisciatello, a spurious inscription forbidding the passage of an army in the name of the Roman people and Senate, the so-called Sanctio, was placed by a bridge on that river. The Quattrocento humanist Flavio Biondo was taken in by it; the actual inscription is conserved in the Museo Archeologico, Cesena. As the centuries went by, several rivers of Italian Adriatic coast between Ravenna and Rimini have at times been said to correspond to the ancient Rubicon.

Present

Today there is very little evidence of Caesar’s historical passage. Savignano sul Rubicone is an industrial town and the river has become one of the most polluted in the Emilia-Romagna region. Exploitation of underground waters along the upper course of the Rubicon has reduced its flow—it was a minor river even during Roman times (“parvi Rubiconis ad undas” as Lucan said, roughly translated "to the waves of [the] tiny Rubicon")—and has since lost its natural route, except in its upper course between low and woody hills.