The Fortress of Sanctuary was Samantha Arias's Kryptonian stronghold located in a desert location. It also serves as a repository for all the knowledge of the Kryptonians, including that of their now-destroyed homeworld of Krypton. After a fight between the Supergirl's team, The Legion, and the Worldkillers, the Fortress was destroyed and turned back into sand.
Samantha Arias followed her newly-acquired beacon's signal to the middle of a desert clearing. All of a sudden, the ground shook and pikes made of rock emerged to form, creating the Fortress of Sanctuary. Samantha went inside the structure and placed the beacon into a Kryptonian computer console panel which caused everything around her to activate. A holographic projection emerged, and told Sam that that this place was her Fortress of Sanctuary, a piece of her dead home world, Krypton.
Reign's version is a blackened cave, with crystal-like rocks protruding from the ground and a dark, cavernous interior.. The Fortress is planted outside somewhere in the desert and is held up by many huge desert-like columns. The interior is dark charcoal in color with pieces glowing red in the darkness. There is a panel which allows carriers of crystal beacons to communicate with a hologram.
- When the Legion's cruiser located the Fortress of Sanctuary, it showed its location on a map of Kazakhstan, rather than the United States, as was previously assumed.