Metamorphoses Book 14: Legends of Early Rome; The Apotheosis of Romulus
Romulus, son of Mars, restored the throne to his grandfather, Numitor. Then in a battle with the Sabines, Juno unlocked one of the city gates of Rome to let the enemy in. Venus saw the open gate and made water nymphs find a way to close it because she couldn't undo the work of another god. After the battle, rule was given to Tatius and then to Romulus. Mars asked Jove to make his son immortal, and so Romulus and his wife were made immortal.