Summertime is a 1955 film directed by David Lean and starring Katharine Hepburn, Rossano Brazzi, and Darren McGavin. Hepburn plays an "old maid" secretary from Ohio who finds romance on a once-in-a-lifetime trip to Italy.
via Internet Archive:
Empire Online gives it 4 out of 5 stars and concludes, "Not one of his best but as the personal favourite of director David Lean's outstanding back catalogue, this is well worth a look." NPR says, "Whatever the film's subtext, Lean intended it to be an affectionate portrait of the city. He became so intoxicated by it that he made it his second home." TCM has some information. Rotten Tomatoes has a critics score of 93%.