…/locations/chromatican_city/undercities.md

Undercities are a network of subterranean, autonomous urban blocks located directly beneath the foundational layer of the Chromatican City.

Structure

Each Undercity spans approximately 225 km², featuring a self-contained ecosystem sustained via surface-pumped air systems, enabling the survival of vegetation and biological lifeforms. Despite their location underground, the Undercities maintain liveable conditions, closely resembling those of the surface-level city.

Access is facilitated through heavily fortified vertical transit shafts, resembling large subway stations, which descend into the depths below. At the terminus of each shaft lies a massive, hexagonal blast door, which bears the designation of the respective Undercity. These gates are permanently sealed to non-authorised lifeforms, and are under continuous surveillance and automated defence.

Connectivity

There are five confirmed Undercities dispersed beneath the Chromatican City. These are interconnected via a network of subterranean tunnels and high-speed metro systems. Each Undercity maintains independent power sources and filtration systems, ensuring operational continuity even in isolation scenarios.