All it took was an ingenious twist on the Fortress of Solitude to prove that Supergirl was far more brilliant than Superman. While being pursued over a crime she didn't commit, Kara Zor-El's variation proved to be the update to the Man of Steel's hideout that Clark desperately needs.
It's one of the oldest assets Superman has to his name; a headquarters located deep in the arctic where Superman stores his most valuable items. Clark's birth father, Jor-El gave his son everything he needed to create his infamous retreat thanks to the crystaline technology of Clark's home planet, Krypton. Superman's iconic Fortress of Solitude not only holds a cache of important information left behind by Jor-El, but mementos from Superman's adventures, as well as important crime-fighting tools, such as the Phantom Zone Projector. Being on the far ends of the Earth might not make the most convenient hiding spot, but for Superman, it's no real issue. But a few tweaks from Supergirl showed how her cousin could majorly improve on his home away from home.
In Action Comics #881 by Greg Rucka, Sterling Gates, and Pere Pérez, Kara Zor-El and her allies Chris Kent and Thara Ak-Var, the new Nightwing and Flamebird, are on the run. The world is convinced that the "Metropolis Three" have killed the city's latest protector, Mon-El, in cold blood after a shady government program known as Project 7734 staged the killing using magic. With heroes and government-backed squadrons attempting to bring them to justice, the trio hightails it to Paris in order to reassess things. They rest in an apartment that Supergirl owns, with the hero admitting she has several little shelters all over the planet, having been inspired by Batman and his satellite Batcaves.
Creating smaller hideouts wouldn’t be the first time Batman has inspired Supergirl in her crime-fighting career, but it does speak to how The Dark Knight helped Kara find her own path separate from Superman. While Supergirl has followed in her cousin's footsteps and tried to be just as good a hero as him, it hasn't always come easy for her. But her twist on Clark's Fortress of Solitude is a great update to an old idea and may show she possesses a more tactical mind than her cousin.
While the idea of one central headquarters has some merit, it’s not exactly ideal for a crisis scenario. Even though Superman’s speed rivals Flash, other factors such as guests may make traveling to the arctic a bit inconvenient. Worse, having one location means there's no safety net for when a villain finds and targets a hero's hideout.
Supergirl's idea to create smaller 'Fortresses of Solitude' builds redundancy into the system and provides options in a worst-case scenario. This sort of thinking gives Kara an edge over Clark, who seems more content with the basic setup. Perhaps Supergirl could put her brilliance to work and show Superman other ways to improve his operation.