This Athenian tetradrachma (an Ancient Greek coin worth four drachmas) bears the helmeted head of Athena on one side and two symbols of the goddess, an owl and an olive-branch, on the other. In Greek mythology Athena, the goddess of wisdom and just warfare, rivalled Zeus himself in power and wisdom. It was Athena who gave the people of Attica the olive-tree. The name of this beloved goddess was given to the chief city of Attica - Athens. The snake and the owl were reckoned to be symbols of her wisdom. The great Greek poet Homer describes Athena as being "owl-eyed". It has been suggested that the eye's of the owl were associated with a very ancient symbol for heaven in the form of a double circle (perhaps from the constellation Gemini that served as a guide to travellers by night).