" Beneath our city lies another city, carved into the earth, a city of hollowness, a city of emptiness, a city of negative space. It's skyline will never be revealed, not until that time in the future when our society's final resting place is excavated and disturbed by a more advanced species. But until that day, we can only know our shadow city piece by piece, by the frail beam of a flashlight, by the touch of a hand in the darkness. "

― , The Sky Is Yours