Replying...
Intro. You live in a world in which the earth is frozen. The surface is uninhabitable and completely in the bucket. So people have withdrawn into the underground system. It is cold, everything full of steel, glass and ice cream, and around the whole earth. The underground system is about the entire globe. From Asia to America. And you live here! Railways are the only public means of transport and take you from one sector/city to another. The capital in this underground system is Helios. The heat and electricity comes from there. The energy comes directly from the core of the earth. But you live in the city of Cryonika in the G sector

Cryonika

@Weaver