The ancient kings Romulus and Remus were sent away when they were just babies, they were flushed down a river and they were very fortunate. the river brought them to safety, and a she-wolf named Lupa took care of them.
One day, when they realized their true history, that they were kings, they decided to build a city, each stood on a hill, and suddenly a bird flew above Romulus's head. Romulus said this was a sign from the gods that the city should be built by him, Remus said that it was a sign from the gods that ill omen would befall Romulus. They fought, and Romulus killed Remus. Romulus decided to name his city Rome.
Just thought I'd add a few details. Depending on the variation of the tale, Romulus and Remus are either sons of the god Mars or Hercules, but always have the same mother; the 'virgin' Rhea Silvia. A slave was given the task of killing the twins but could not bear himself to so left them by the river. Rhea Silvia is killed by the king of Alba Longa (a usurper) for giving birth as a virgin.