Cimmeria was designated by the High Council of the Asgard as a safe world for developing sentient species by unanimous decree, era 40.73.29. Thor's Hammer protects Cimmeria from the Goa'uld, and the sign of Thor's Hammer has become a symbol of the planet. All Jaffa and Goa'uld were forbidden to go there because of something that had transpired on Cimmeria that no Goa'uld would speak of. A forested and mountainous world, it is home to the Cimmerians whose ancestors were brought there from Earth by Thor. SG-1 had been forced to destroy Thor's Hammer to free Teal'c, leaving Cimmeria vulnerable to attack by the Goa'uld. Heru'ur invaded the planet and killed over half of the population before intervention by SG-1 and the Asgard could defeat his forces. Thor's Hammer has since been replaced to protect the planet once again.
Cross Reference: Asgard, Cimmerians, Etins, Gairwyn, Hall of Mjollnir, Hall of Thor's Might, Heru'ur, Kendra, Olaf, Protected Planets Treaty, Runes, Thor, Thor's Hammer
Episode Reference: Thor's Hammer, Thor's Chariot