At any time between 1900 and 1905, if Ravel had been successful in his attempts to win the Prix de Rome, he could have found himself based in the Italian capital for two or three years of study and writing. As it turned out, there was to be a surprisingly long delay before his first recorded trip to Italy. In 1922 Ravel travelled to Milan to take part in a concert of his works on 1st November, which was organised by the Istituto del Convegno (Orenstein  letter 205, and note). This concert included the first Italian performances of his Sonate pour violon et violoncelle and the Berceuse sur le nom de Fauré. After this engagement, Ravel took the opportunity to make a visit to Venice (Marnat  p.528).
Ravel was in Italy again in April 1923 for a concert in Rome (Orenstein  letters 215 and 218), further details unknown.
In March 1926 Ravel was stating his intention to go soon to Milan for the final rehearsals of L'Enfant et les sortilèges (Orenstein  letter 265). But principally on his mind at this time was the completion of the Chansons madécasses in time for their first performance at the American Academy at Rome, on the afternoon of Saturday 8 May 1926. (Marnat  p.772-773). (But it is not clear whether Ravel was actually present at this occasion.)
Italy does not appear to have featured in any of Ravel's subsequent concert tours.