Prometheus was punished by Zeus after he gave humans fire and taught them the basics of civilization. Some say Prometheus was the savior of humanity and raised us above the beasts.
Prometheus' punishment for helping humans was to be chained so that an eagle would fly down and eat his liver every day and then every night his liver would grow back. Prometheus is immortal and cannot die, so he suffered like this for hundreds of years before he was released by Heracles.
Depending on who you talk to Prometheus was chained to a mountain or a boulder… and this is the controversy that has many people divided.
I think it is vital that this controversy be resolved so people can properly recognize Prometheus' sacrifice.