The Ancient outpost in Antarctica contained a small stasis chamber which O'Neill, using the knowledge of the Ancients, described simply as "dormata" ("sleep"). O'Neill had interfaced with the Ancient repository, which downloaded an alien database into his mind, and he had activated the Ancient defense weapon which had destroyed Anubis and saved Earth, but the technology had weakened him to the point of death. SG-1 placed O'Neill into the stasis chamber where he remained in cryogenic suspension until Thor was able to use Asgard technology to revive and restore him. The stasis chamber has remained in Antarctica, and the SGC has mastered the technology and maintained control of the device which can be used to preserve or release an individual from stasis. When Daniel was transformed into a Prior and was considered a threat to Earth, the IOA made arrangements to have him preserved in the stasis chamber in Antarctica until the threat had passed, however Daniel escaped from custody before that could happen.
In an underground laboratory on P3X-584, SG-1 discovered another stasis chamber in which Khalek had been preserved. The lab belonged to Anubis but was based on Ancient technology, and like the stasis chamber in Antarctica, Khalek had been placed in a standing position, sealed inside by a translucent wall that gave the impression of a sheet of ice.
When SG-1's search for Merlin's weapon brought them to Merlin's cave on an isolated world, they discovered Merlin himself in an Ancient stasis chamber. The plaque beside the chamber read, "Here lies Myrrdin, Archmage of the Round," and there he had slept in cryogenic suspension for well over a thousand years. According to myth, Morgan Le Fay had trapped Merlin in a cave and had left him frozen there for all eternity, but in reality she had sought to protect him and his creation from the Ancients. As the Ancient repository on the wall activated, it seemed to trigger the stasis chamber, and the greenish translucent seal, like a wall of ice, instantly vanished, and Merlin tumbled out. He revived slowly, but his body had been too greatly weakened from centuries in stasis, and he uploaded his knowledge into the repository so that Daniel could continue his work after he died.
Cross Reference: Ancients, Ancient Defense Weapon, Ancient Outpost, Ancient Repository, Khalek, Merlin, Merlin's Cave, Jack O'Neill, P3X-584, Stasis
Episode Reference: Lost City, Prototype, The Quest