Ras Kasaroun (Arabic: راس كسرون)[1] or El-Kas (Arabic: القاس), also known as Casius Mons in Latin, or Kasion Oros (Ancient Greek: Κάσιον)[2] to Greek geographers such as Herodotus (who considered it to mark the boundary between Egypt and Syria), is a small mountain and a former town near the marshy Lake Bardawil, the "Serbonian Bog" of Herodotus, where Zeus' ancient opponent Typhon was "said to be hidden".

[3] Here, Greeks knew, Baal Sephon was worshipped.

The sandy mount stands out about the flat landscape, though it is a mere 100 metres above the sea.

Like the other Mount Casius in Syria, it was historically associated with a shrine to Zeus, one of whose epithets was Kasios.

The saying "Kasiotic knot", which in Medieval Greek meant "someone who are crooked in their ways", comes from the town's name.