(at around 1h 28 mins) Vittoria and Piero get wet from a sprinkler. The right side of Piero's jacket is wet. A minute later when they are listening to the piano player, the back of Vittoria's blouse is still wet, but Piero's jacket is dry.
When Vittoria and Piero are approaching the corner where they stop to talk and Piero leans against the fence, a whitish mark from the fence can be seen across the back of Alain Delon's suit jacket, evidence of a previous take.
At 1:42:38 the microphone enters the frame (bottom left)