We don’t know much about the Omniums other than that the original ones were factories that produced the Omnics and other automated robotic machinery. The Omnium in Australia was given back to the surviving Omnics after the Crisis and suppose to be a long-term residence for Omnics in that region as part of a peace agreement between Omnics and the Australian government. Roadhog’s biography states:
So its vague and we really don’t have a good idea of what an Omnium exactly looks like, we obviously see parts of it in Junkertown (especially section 3, the Arena), and I think the new command ship in the Rio De Janeiro Map for Overwatch 2 showing the factory assembly of the new Null Sector units gives some interesting insight. Still, we have yet to see a full Omnium intact, but I believe the ones in North America and Russia still stand. We also know there is an underwater Omnium in the South China Sea just off the coast of South Korea, but it is uncertain if that was originally a true Omnium or something constructed during the crisis.
This is more appropriate for Story Discussion. To move a topic, click the pencil icon in your starting post and change the category in the dialog.