According to the information that Mara managed to 'extract' from the thugs we faced, the factory was abandoned after some explosion or something destroyed most of the building.
This gang then went ahead to claim the building for themselves and made it one of their hideouts.
Even though I say 'building', it really is just a network of rooms linked together by some corridors that were under the station's ground floor.
To get there, we had to take an elevator down to an underground corridor that we had to navigate to get to the entrance.
It was supposedly the perfect place for them because the factory itself was made to manufacture illegal weapons so it was already built in a secluded location out of view from everyone else.
Unfortunately, that means that we would be primarily fighting in close quarters so Lea would not be able to set up somewhere to watch over us from a distance but instead, follow us into the building.