Rio de Janeiro, or simply Rio, was a city in Brazil, South America, Earth
In 2365, a holoprogram available to crewmembers of the USS Enterprise-D was "Carnival Celebration – Rio de Janeiro, Earth". The program, with a code list number of 05-865, was listed in the exercise menu. (TNG: "The Emissary", okudagram)
In 2375, Ezri Dax mentioned that Jadzia was fond of Rio, when Miles O'Brien was contemplating places to live upon moving back to Earth. (DS9: "What You Leave Behind")