The Sterile Earth bunker is an underground shelter formerly used by future humans, including Matt Anderson and his father Gideon. When Matt returned to the area years later with Connor Temple and Abby Maitland, he used the now-abandoned shelter to hide from Mutated Future Predators.
The bunker is fairly accessible with a large chain that marks the bunker. To get in, you simply lift a large metal trap door. The bunker has an electrical system that is powered by a small generator. There are rows of shelves contain vital supplies for survival, namely water, the water gets poisoned over time, as Matt was taste-testing the water before finding a clean one for Connor to drink. The people of the Sterile Earth move from shelter to shelter.
To seek shelter from the toxic storms on the surface, Matt takes Abby and Connor to an underground bunker. He explains that he and his people would nomadically move from shelter to shelter, as only the Mutated Future Predators can survive the surface's frequent poisonous storms.