Neptune originally was the Roman god of freshwater, including rain and fertility. Later in 399 BCE Neptune become identified with the Greek sea god Poseidon. His wife was Salacia.
The powerful and militaristic Romans eventually made Greece a province of Rome in 146 BCE but they were strongly influenced by the rich depth of Greek myth and culture.
So depictions of Neptune in mosaics, especially around North Africa, were strongly imbued with Greek aesthetics.
Like the Greek Poseidon, Neptune was additionally worshipped by the Romans as Neptunus Equester, the god that overlooks horse-racing.
Also from the Greek tradition, Neptune was the brother of Jupiter and Pluto. The three brothers governed the heavenly, earthly and underworld realms.
Neptune had two main temples of worship in ancient Rome. His festival was celebrated mid-summer when huts were made out of tree branches and underbrush.
Scholars mostly agree that the symbolism of these structures pointed to Neptune’s role as the giver of life through water.
Bernini’s magnificent sculpture of Neptune and Triton can be seen at the Victoria and Albert Museum, London. And many other depictions of Neptune are found around the world, as the one pictured here (top right) at Coney Island, New York.
Anyone who has delighted in Gustav Holst’s masterpiece, The Planets, will remember that Neptune is the 7th and final movement, subtitled “The Mystic.” Here, Holst brilliantly merges the mythical and astronomical aspects of Neptune.
Concerning astronomy, Neptune is the name of the 8th and, since the demotion of Pluto in 2006, furthest planet from our sun.