I was in Italy in Novemeber and came across two of his works. One was the Tribunale di Messina -- Messina courthouse. The project began in 1912 but the Great War interrupted work until the early 1920s. It was completed in 1927 and dedicated the following year.
The other was the former Bank of Naples building renovated by Piacentini in 1939 for the 400th anniversary of the creation of the bank (which has gone through many name and management changes: it's now Intesta Sanpaolo). Some background is here.
They are of interest because they bookend the era of what is called "Fascist Architecture," a term I find somewhat misleading. The basic style is similar to the stripped-down ornamentation buildings found in non-fascist countries such as the United States in the 1930s.