During the fight scene when she literally kicks him out of the house, she kicked so hard she broke her foot.
The Italian crew was so upset over the assassination of Robert Kennedy which occurred during the shoot that they dedicated an extra hour of work in his memory.
The secret, as in this movie's title, The Secret of Santa Vittoria, was that Italian villagers during Nazi German occupied Italy during World War II were able to keep secret from them one million bottles of wine which were hidden underground.