Page "Balor" Paragraph 4

One legend tells that, when Balor was slain by Lugh, Balor's eye was still open when he fell face first into the ground.

Thus his deadly eye beam burned a hole into the earth.

Long after, the hole filled with water and became a lake which is now known as Loch na Súl, or " Lake of the Eye ", which is to be found in County Sligo.