When you reach the Villa San Giovanni (on the ‘toe’ of the Italian ‘boot’), the train is disassembled for the ferry that crosses the Messina straight.  Then it’s reassembled for the onward journey on the island of Sicily.  I’ve done it with my parents, and it was fun, but I’m not a huge fan of train travel in Sicily so I probably won’t do it again.  Still, it’s a unique experience!