"In Greek mythology, perhaps no hero is so enduring as Herakles, and his victory over the lion – the first of his twelve labors – clearly associates him with Nemea. Since the skin of the lion was impenetrable, Herakles had to wrestle the lion and strangle him. Then, with the lion’s own claws, Herakles skinned the beast, thereafter wearing the skin over his back as a kind of armor (Alexander the Great adopted this same iconography in his coins). One reads in general handbooks and guides that Herakles, as a thanksgiving to his father Zeus for his victory over the lion, established the Sanctuary of Zeus and the games. However, the only archaeological evidence of the myth, discovered at Nemea, consists of small bronze lion’s head attachments and a gold foil relief representation of Herakles’s face with the lion’s skin tied under his chin. The paucity of evidence is not surprising, however, for the connection between Herakles’victory over the lion and the foundation of the Nemean Games is first mentioned in ancient literature no earlier than the 1^st century AD."

from
NEMEA, a guide to the site and museum, Stephen G. Miller and other, Athena 2004, page.34 up