The founding of Rome
Romulus and Remus are the twin brothers of Rhea Silvia, the daughter of Numitor. He was the legitimate king of Alba Longa, a city-state founded by no less than the son of Aeneas, the son of Venus whose adventures were told in the Aeneid. Numitor had been exhiled by his evil brother Amulius, who forced Rhea Silvia to become a Vestal, a virgin priestess, in order to prevent her from having a son who could claim the throne. The girl was however so pretty that the god Mars wanted her so bad that he raped her in a sacred grove. The result of this encounter were Romulus and Remus, so Amulius ordered Silvia to be drowned (but she was resurrected by the piety of the waters themselves), and the kids to disappear by a rather convoluted plan. They were to be put in a wicker basket, then taken by a slave to the Aniene river and just left floating away. Surprisingly, the children survived and the basket got beached beside the Palatine hill, close to a grotto called Lupercal, where the wolf-god Lupercus was worshipped.
Now under the protection of Numitor and recognized as noblemen, Romulus and Remus moved out of Alba Longa to found their own city on the shores of the Tiber river. Problem was, since they were twins it was not possible to choose the older brother as the one founder, as it was customary in those times. To decide who the founder and namer of the new town was to be, each young man went up one hill (Romulus on the Palatine, Remus on the Aventin) and waited for a sign of the gods. Remus saw six vultures first, but Romulus saw twelve a little later: as push came to shove, Remus got killed by his brother. Thus Romulus got the naming rights, and Rome was founded.