The Underground Fortress served as the military's headquarters on the planet of Aquilae.
To get into the fortress from above ground, one had to go through a concealed entrance: a sliding door hidden within a rock wall situated in a tight canyon.
The Aquilaeans detonated atomic warheads inside it, resulting in its annihilation. This was done to keep the Galactic Empire from acquiring their genetic and biological information. Everyone within perished, including Queen Breha. Leia, along with her brothers and General Luke Skywalker, were located outside the fortress, and they managed to flee to Gordon.
Although portrayed here as a defensive act of self-destruction, the fortress's destruction was reworked into the annihilation of Ogana Major in the screenplay's second iteration. Later on, it served as inspiration for the destiny of Alderaan.
- The Star Wars rough draft
- The Making of Star Wars: The Definitive Story Behind the Original Film