The Dead Sea in Israel on Earth was both the lowest body of water on the planet and the lowest point on the Earth.
It was rich in salt and attracted the attention of the Ronans who, towards the end of the Stone Age, attempted to drill beneath it and warm up the planet by releasing the heat from the planet's core. When the caves were flooded by the sea water, trapping the Romans underground, the Dead Sea was emptied until it was refilled by water from the River Jordan. (PROSE: The Heat-Seekers)