Lanuvium (more frequently Lanivium in Imperial Roman times, later Civita Lavinia, modern Lanuvio) is an ancient city of Latium (Latin: Lānŭuĭum or Lānĭuĭum), some 32 kilometres (20 mi) southeast of Rome, a little southwest of the Via Appia.
Situated on an isolated hill projecting south from the main mass of the Alban Hills, Lanuvium commanded an extensive view over the low country between it and the sea. According to the legend, it was founded by Diomedes, or by one Lanoios, an exile from Troy. The first documented traces of the settlement date from the 9th century BC and by the 6th century BC it was part of the Latin League.
The city warred against Rome at the battles of Aricia (504 BC) and Lake Regillus (496 BC), as well as in 383 and 341 BC, mostly with negative outcomes. Rome conquered Lanuvium in 338 BC; at first its denizens did not enjoy the right of Roman citizenship, but acquired it later. In imperial times the city's chief magistrate and municipal council kept the titles of dictator and senatus respectively.
Lanuvium was especially noted for its rich and much venerated temple of Juno Sospes (Livy 8.14; Cic. Nat. D. 1.83; Fin. 2.63), from which Octavian borrowed money in 31 BC, and the possessions of which extended as far as the coast of the Mediterranean. It possessed many other temples repaired by Antoninus Pius, who was born close by (S. H. A. Ant. Pius 1), as was Commodus. Other people who sojourned in Lanuvium include Marcus Aemilius Lepidus, Marcus Iunius Brutus and Marcus Aurelius. One prominent native of Lanuvium was Lucius Licinius Murena (consul of 62 BC) whom Cicero defended in late 63 BC. Others include the actor Roscius (Cic. Div. 36) and the Roman people's tribune of 57 BC, Titus Annius Milo, who served as the city's dictator in 52 BC (Cic. Mil. 27).
The edict of Theodosius I (391 AD), which made Christianity the sole religion of the Roman Empire, caused the decline of the city and it was later abandoned.
Remains of the ancient theatre and of the city walls exist in the modern town, and above it is an area surrounded by a portico, in opus reticulatum, upon the north side of which is a rectangular building in opus quadratum, probably connected with the temple of Juno where archaic decorative terracottas artifacts have been found. The acropolis of the primitive city was probably on the highest point above the temple to the north. The neighborhood, which is now covered with vineyards, contains the remains of many Roman villas, one of which is traditionally attributed to the Emperor Antoninus Pius.