Flag of Cloudsdale

Cloudsdale (officially "The Semi-Autonomous Pegasus City of Cloudsdale") is unique among Equestria's cities for two reasons. First, it moves. In it's mission to deliver weather to all parts of Equestria, the city is constantly mobile. This means it cannot be part of any province, so it governs itself as a sort of city-state. Secondly, it is home only to pegasus ponies. The city's airborne nature means unicorns and earth ponies can only visit for short periods, and even then only with the aid of powerful magic. This poses a problem, as one of the founding principles of Equestria was a ban on segregation. Since the city's weather factories provide an essential service, the city can't be disbanded, so instead all pegasi born in Cloudsdale must leave for five years and see the rest of Equestria when they become adults. About two thirds return to live in the city permanently.

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This one has a lot of real-life symbolism.