traditionally the fourth king of Rome, from 642 to 617 BC. The details of his reign, provided by Roman historians such as Livy (64 or 59 BC–AD 17), must be regarded as largely legendary—e.g., the settlement of the Aventine Hill outside Rome, the first extension of Rome beyond the Tiber River to the Janiculum Hill, and the founding of the port of Ostia at the mouth of the Tiber.