Numa
Noted for his justice and piety (this coin of 97 BCE shows Numa about to sacrifice a goat), Numa Pompilius, a learned man from the Sabine town of Cures, was chosen by the Senate and the Roman people to be the second King of Rome (715-673 BCE) after Romulus and a one year interrex.
To him the Romans attributed a long list of religious and cultural institutions, such as organization of the priestly colleges, the creation of the Pontifex Maximus, the establishment of the Vestals (see G.Cesari's Numa Pompilius Establishing Worship of the Vestals), the calendar of festivals, and the construction of the Regia. Livy, however, calls his greatest gift to the Romans his achievement of peace with neighboring territories (see Livy, Ab Urbe Condita 1.18-22 and Plutarch's Life of Numa).