This is most likely the location of the "Super Ark" the Visionary was in. He has set up this place as a strategical advantage most likely because of its remoteness to Subway Town, Wellspring, Dead City and the remains of Crescent City. Cross himself most likely used it due to the "Super Ark's" power. As it happens, in the end Nicholas Raine will have to infiltrate this facility and insert the codes provided by the Resistance in order to trigger the emergence of the remaining Arks around the world.