THE UNDERGROUND METROPOLIS
From the moment humanity was forced to take refuge underground, few cities remained open to the sky, polar cities being notable exceptions. With the disappearance of vegetation, air quality deteriorated and oxygen availability was drastically reduced. In response to this challenge, glass domes arose that housed greenhouses and laboratories, providing a controlled environment.
Most of the habitable areas were underground, connected by intricate tunnels that facilitated the movement of inhabitants through an advanced transportation system: the hyperloop, a special train that used magnetic levitation to move efficiently. This ingenious system effectively connected the different underground communities, creating an interconnected network that facilitated mobility and collaboration between the inhabitants of these underground cities.