Rio Tinto is a Portuguese city and parish, located in Gondomar Municipality, in northern Portugal. The population in 2011 was 50,713…Rio Tinto is a Portuguese city and parish, located in Gondomar Municipality, in northern Portugal. The population in 2011 was 50,713, in an area of 9.38 km². Rio Tinto, which in Portuguese means red river, was elevated to city status in 1995, and the city of Rio Tinto includes two parishes: Baguim do Monte and Rio Tinto, with a total of 65,000 inhabitants, being the most populous city in Gondomar municipality, and third largest in the Greater Porto agglomeration.