This scene shows us this world might co-exist with ours in every cities of the world. And also probably referenced from the Victorian Underworlds, where people from the higher class could leave their true identity on the surface, and do what ever they want in the underground, a double life.
Thoughts: This is a theme that I've been fascinated about since starting this project, as it seems people are leaving their normal lives and leading a second persona in this underworld. Therefore the city is disappearing, as rules are too restricting for these people to do what ever they want, so they go to a different world where they are free to do what they can't do above.