Late at night, a gate in the south of New Roman City quietly rose. The inner and outer layers of the armored door can withstand the direct impact of the missile, which is due to the importance the city attaches to defense. There is a hollow environment between the earth's crust and the rocks of this underground city. It was connected by an extremely large number of metal objects. These things are both a supporting node between the city and the earth's crust and a powerful defensive ...