Greek Myths? What is the name of the river into the Underworld?

I know someone already said it but there were 2 dif. answers so which is it?

Greek Myths? What is the name of the river into the Underworld?
The river Styx.
Reply:Styx, stix sticks stixs stixes stixexs. Either way you say it, it's gonna be styx.
Reply:Styx. And the Greek Myth underworld is called Hades.
Reply:In GREEK mythology it's called the River Styx.
Reply:The River Styx
Reply:Here is a website for you!
Reply:Styx
Reply:River Styx. Called like the immortal river or something like that. Charon is the boatman.