Rome's founding legend hinges on a bird-counting contest the twins could not settle
Romulus and Remus agreed to let the gods pick the site of their city. Remus saw six vultures first over the Aventine; Romulus then saw twelve over the Palatine. One claimed priority, the other numbers, and the quarrel ended with Remus dead. Romans marked the founding every April 21.
The legend starts with a usurpation. Amulius seized the throne of Alba Longa from his brother Numitor and made Numitor's daughter, Rhea Silvia, a Vestal virgin to stop her bearing heirs. She became pregnant anyway, naming the war god Mars as father. Ordered to drown the twins, servants found the Tiber too swollen to reach and left them under a fig tree below the Palatine, where a she-wolf nursed them until the herdsman Faustulus and his wife took them in. Grown up, the brothers killed Amulius and restored their grandfather before setting off to found a city of their own.
Accounts of Remus's death vary. In one, Romulus ploughed a square furrow for the walls and Remus leapt over it in mockery, provoking a fatal blow; in another he fell in a brawl along with Faustulus. Once king, Romulus is credited with Rome's basic machinery: three tribes, each split into ten wards that supplied a hundred foot soldiers and ten horsemen, a council of city fathers whose descendants became the patricians, a ban on infanticide and a sanctuary on the Capitoline where fugitives could seek citizenship.
That sanctuary created a population of mostly single men, and neighbours refused intermarriage. Romulus staged a festival, and at a signal the Romans carried off the young women among their Sabine and Latin guests. The Latin towns attacked piecemeal and lost; Romulus killed the prince of Caenina in single combat, becoming the first to dedicate the spolia opima. The Sabines under Titus Tatius took the citadel through the betrayal of Tarpeia, but the abducted women themselves stepped between the armies and forced a peace, after which the two kings shared power.
After 37 years on the throne, Romulus is said to have vanished in a sudden storm while reviewing troops. Livy records rumours that senators murdered him, but preferred the version in which Mars carried him to heaven. He was later worshipped as the god Quirinus, and the next king, Numa Pompilius, was chosen from among the Sabines.
Source: Romulus