Journey into Mystery Annual #1

Thor and Loki come across a pair of storm giants attacking the gateway from Asgard to Olympus. During the ensuing battle, Thor is accidentally transported to the fabled land and finds himself in combat with the mighty Hercules with neither party willing to back down. After a titanic battle, Zeus stops the conflict and proclaims them both worthy allies and friends. Thor is sent back to Asgard and Zeus closes the passage forever.