Terracina is located at the southern edge of the Agro Pontino (an approximately quadrangular area of former marshland in the Lazio Region, extending along the coast), south of the Circeo promontory, towards the mouth of the Amaseno river on the Tyrrhenian coast, and develops from a branch of Monte Sant’Angelo to the Lungomare Circe.
Terracina appears in ancient sources with two names: the Latin Tarracina and the Volscan Anxur. The latter is the name of Jupiter himself as a youth (Iuppiter Anxur or Anxurus), and was the tutelary god of the city, venerated on the Mons Neptunius (current Monte Sant’Angelo), where a temple dedicated to him still exists.
The name Tarracina has been instead pointed out variously as pre-Indo-European origin (Ταρρακινή in ancient Greek), or as Etruscan (Tarchna or Tarchuna, the name of the Tarquinii family): in this view, it would precede the Volscan conquest.
Terracina occupied a position of notable strategic importance: it is located at the point where the Volscan Hills (an extension of the Lepini Mountains) reach the coast, leaving no space for passage between them and the sea, on a site commanding the Pontine Marshes (urbs prona in paludes, a city surrounded by marshes, as Livy called it) and also possessing a small harbour. During the 7th century BC, it joined the Etruscan League of twelve cities. In 509 BC Terracina was already under Roman supremacy as reported in the first treaty between Rome and Carthage. It was soon re-occupied by the Volscans and was not included in the list of the Latin League of 499 BC. In 406 it was recaptured by the Romans, then lost in 402 and recovered in 400, unsuccessfully attacked by the Volscans in 397, and finally secured by the establishment of a colony of Roman citizens in 329 BC as Colonia Anxurnas.
As a colonia maritima it frequently appears in history. The construction of the Via Appia in 312 BC added to its importance: the road at first crossed the hill at the back of the promontory by a steep ascent and descent. An attempt was made in 184 BC to get round it by an embankment thrown out into the sea: but it was probably not until early in Trajan’s time that a cut in the rocks at the foot of the promontory (Pisco Montano) finally solved the problem. The depth of the cut is indicated by marks on the vertical wall at intervals of 10 Roman feet; the lowest mark, about 1 mt above the present road, is CXX, corresponding to 36 metres (118 feet).
It was probably in consequence of this road cut that some of the more important buildings of the imperial period were erected on the low ground near the small harbour. The construction of the coast road, the Via Severiana, from Ostia to Terracina, added to the importance of the place. The Via Appia and the Via Severiana met some few miles east of Terracina, and the Via Appia then traversed the pass of Lautulae, between the mountains and the Lake of Fondi, where the Samnites defeated the Romans with losses in 315 BC. The beauty of the promontory with its luxuriant flora and attractive view had caused it to be frequented by the Romans as early as 200 BC.
Terracina became an important centre for the development of the fertile valley lying to the west, and started to grow new settlements at the foot of the hill which turned into a sanctuary area with some patricianmansions.
New public edifices were erected starting from the time of Lucius Cornelius Sulla including a new theatre and forum, while the sanctuary was renovated. Marcus Favonius, the imitator of Cato the Younger, was born in Terracina, as was the emperor Servius Sulpicius Galba (in 3 BC); both Galba and Titus Flavius Domitian possessed villas in the area.
The port was built under Trajan and Antoninus Pius in the 2nd century AD. The last Roman construction was that of a new line of walls during the 5th century AD.
The nearby mineral springs by the coast, known to the Romans as Neptuniae aquae and later renamed Acqua Magnesia, are still in use, except one containing arsenic which was blocked up both by the ancients and again in 1839 as a precaution.