Halion Complex

Basically an entire facility made to benefit the survival of humanity if anything bad happens, like meteor showers, nuclear explosions, volcanic explosion, antimatter catastrophe, and other disasters, the whole facility is for improving the benefit of survival, when a pandemic happens they have to let any humans who aren't infected by the disease in, and seal up the facility and the air shafts. And seal up the facility when it's not in use. This is until a catastrophic event happened that a volcano exploded then caused an entire endless ice age in the year 2065.