The city is organized vertically, adhering to a strict socio-economic hierarchy based on gravity:
Household items are repurposed on a massive scale.
The film uses the city to satirize the British class system.
Unlike the flat, grid-like structure of American sewer systems, Ratropolis is a vertical, cavernous city built within the circular drainage tunnels of Victorian-era London. The architecture is a chaotic yet functional amalgamation of pipes, arches, and ledges.
Ratropolis is not just a shantytown; it is a fully functioning society with a distinct culture that mimics—and arguably improves upon—the human London above.
While the film uses this setting for comedic effect, the city itself is a masterpiece of production design—a character in its own right. It represents a scrappy, affectionate mirror image of London, built from the discarded dreams and debris of the human world "Up Top."
Some viewers find the shift in tone, particularly from the beginning to the more action-oriented and darker middle and end, to be jarring. The pacing can also feel uneven.
The film does not lack in action sequences. From the initial chase through London to the adventures in the sewer, there's a good pace that keeps the viewer engaged.
For Roddy, the city represents a terrifying fall from grace—a world of slime and smell. However, as the film progresses, Ratropolis reveals itself to be a place of vibrant life, community, and excitement. The city validates the idea that a "flushed" life is not a wasted one. The items that humans deem trash are treasured in Ratropolis, mirroring the character arc of Roddy himself: a lonely "pet" who finds purpose and family in the underworld.