Othala was a planet located in the galaxy of Ida (presumed to be the Asgard's home galaxy), and is one of the primary worlds within the sphere of the Asgard control and the capital planet of the Asgard race until it was evacuated.
About the planet
Othala from space.
Othala served as the headquarters for the Asgard High Council, which convened within Gladsheim. The Stargate was located in a meeting chamber within the Great Hall that served as a focal point of contact with the other members of the Great Alliance, and could only be accessed by members of this alliance. The Asgard were given a device by the Ancients that alerted them when the Stargate was activated, which had not occurred for millennia until Colonel Jack O'Neill's arrival, and also informed them to how many travelers were present on the journey. This allowed the Asgard to prepare for the arrival of the visitors who were met by the guardians of the Stargate.
Othala was seen in detail when Major Samantha Carter visited the world to help Thor devise a way to defeat the Replicators. (SG1: "Small Victories")
The rest of the planet was a hive of activity and contained numerous meeting halls, construction facilities, homes, academic centers and outposts of the Asgard's military. Several green parks separate the planet-sized city. It has been noted that while a majority of the inhabitants are Asgard, it is possible to notice a few members of other species. (RPG: "Friends and Foes: Stargate Season Two")
History
After Colonel Jack O'Neill succumbed to the Ancients' Repository of knowledge downloaded into his brain, his subconscious mind carried out the necessary tasks to get him to Othala, where he was able to get help. (SG1: "The Fifth Race")
As a result of the war with the Replicators, the Asgard were forced to evacuate Othala and move to Orilla, while destroying Othala, and the important Asgard colony Hala in the process, with a black hole. (SG1: "New Order, Part 1")
Background
In Old Norse, "Othala" is the word meaning "estate" (rough translation); there is also a rune of the same name. It appears at the bottom of the Asgard text in Heliopolis. (SG1: "The Torment of Tantalus")