The Alishan Narrow-Gauge Railway (阿里山小火車) is one of the more popular and famous methods of getting around Alishan. It is one of the five famous sights there; it is also rickety but overall a pleasant ride. Tickets (I believe) are NT 50, or at least from Sacred Tree back to Alishan Main Station. Trains chug between stations at Alishan Main station, Sacred Tree, Jhaoping, and Jhushan. Cars are generally small and sometimes crowded. Trains are also relatively infrequent; check the schedule before you head out if you plan to ride one.
During the trip, you will hear music and a brief instruction through the broadcast.
When the train stops at every small station for about 2 minutes, you can choose some to get off and take a picture.