Origin
Poseidon is a son of Cronus and Rhea, swallowed at birth then freed by Zeus. When the world is shared, he receives the sea. Armed with a trident forged by the Cyclopes, he can raise storms, shake the earth or calm the waves.
The story
He competes with Athena to become the protector of a great Greek city. With a blow of his trident he brings forth a spring of salt water; Athena offers an olive tree. The people prefer the olive tree, and the city takes the name of Athens.
His anger is fearsome. When Ulysses blinds the Cyclops Polyphemus, who is his son, Poseidon pursues him with his grudge through ten years of wandering. The Romans identified him with Neptune, an old god of fresh water who became master of the sea.
The symbol
Neptune is the first planet found by calculation before being observed: the astronomer Le Verrier predicted its position in 1846, and it was seen through a telescope a few days later. It has the fastest winds in the solar system.
In astrology, Neptune stands for dreams, intuition, imagination and compassion, but also haze and illusion. It is seen as the modern ruler of Pisces.