Which city's sky is represented by the stars on Brazil's flag?

The stars on Brazil's flag represent the sky over Rio de Janeiro. More precisely, the blue globe depicts the stars as they appeared over Rio on the morning of 15 November 1889, the day Brazil's republic was proclaimed.

The design is an astronomical snapshot rather than a generic collection of stars. It includes constellations such as the Southern Cross, and each of the 27 stars represents a Brazilian federative unit: the 26 states and the Federal District. The stars are arranged according to a celestial view and are shown as if observed from outside the celestial sphere.

A common mix-up is to assume the stars represent Brasília, Brazil's present-day capital, because Brasília is the Federal District. However, the flag's sky refers to Rio de Janeiro, which was the capital and the location associated with the republic's proclamation in 1889. The Federal District is represented by Sigma Octantis, the star near the south celestial pole.