According to a reference list - published 1927 - from the German company Mix & Genest AG, Abteilung Rohrpost und Förderanlagen in Berlin-Schöneberg, the Italian city of Naples had access to a Pneumatic Tube Mail system with ten stations and a tube length of 17 kilometers.
Reference list Mix & Genest - June 1927Posta Pneumatica Napoli Centro 1928-04-05 Frontside envelopePosta Pneumatica Napoli Centro 1928-04-05 Backside envelope
Pneumatic Tube, Rohrpost, Buizenpost