Born Nais Louisiana Gattella in Rijeka (at the time the Italian city Fiume), after studying in Trieste she moved to Rome, where she made her film debut appearing in two tiny roles in Goffredo Alessandrini Seconda B and Alessandro Blasetti"s 1860. Lago later attended the Centro Sperimentale di Cinematografia, graduating in 1936. She then devoted herself to the theater, entering the major stage companies of the time.