The Sixth Vial
The River Euphrates Dried Up
Revelation 16:12

"And the Sixth Angel poured out his Vial upon the Great River Euphrates; and the water thereof was dried up, that the way of the Kings of the East might be prepared."

        This means the literal river Euphrates dried up like all the other plagues are literal.  It is to be dried up so the Kings of the East and their armies can cross over and ready themselves for the Battle of Armageddon.