Every water that moves, from the spring to the open sea.

Neptune began as a god of fresh water in a dry summer land and grew to hold the sea as Rome grew to sail it. His festival, the Neptunalia, fell in the parching heat of late July, when water mattered most, and a temple stood to him in the Campus Martius by the Circus Flaminius. As Neptunus Equester he also kept horses and horsemanship, which is why the races belonged to him too.

The eighth planet took his name on its discovery in 1846.