Ushuaia is the capital of Tierra del Fuego, Antártida e Islas del Atlántico Sur Province, Argentina. With a population of 82,615 and a location b…Ushuaia is the capital of Tierra del Fuego, Antártida e Islas del Atlántico Sur Province, Argentina. With a population of 82,615 and a location below the 54th parallel south latitude, Ushuaia claims the title of world's southernmost city.