Jennifer Y.
Yelp
For people that are not local and unfamiliar with Alishan, it's best to do your research before coming. They restrict only official shuttles and vehicles to go inside the park, otherwise you must park outside and walk into it. There are only two hotels that are built within the park itself and neither are luxurious, just fine. Many people book stays outside at neighboring towns and ride the train in too as an alternative. Taking a car in, from the Chianti High Speed Rail Station, it is about a 2 hour ride with very winding and narrow, difficult roads uphill in the mountains-I would advise against doing this drive yourself unless you're experienced.
The park itself is beautiful, the temperature is cooler since it's higher, so make sure to bring layers just in case it's a cooler day. It tends to also potentially rain due to being so high up in the clouds, so it's good to bring rainwear/umbrellas. The shops will have some if you forget them, plus some layers and coats/shawls.
You will need more than one day if you want to do all of the park, there are many stairs and you should allow for time for rest and breaks. Don't forget your water and hydration! There are trains within the park, but they only go back into town by the Alishan station outside-none of them run to different parts of the park. The last of these trains will run around 4:30pm.
The most notable places are the sacred trees and I recommend the walk along the old rails trail that leads to one of the trees, along with the northwest part of park with the official 'sacred tree'-that trail is easier since it's going downhill and you can end with taking the train into town. The sunrise/sunset is very popular to watch as well, but you have to be able to time it right and weather conditions are not always favorable-so don't expecting to see the 'sea of clouds' if nature doesn't cooperate. To see the sunrise you also have to show up extremely early and book your train ticket in advance to be at the viewpoint deeper into the park.
The small village around the park has some restaurants and small souvenir shops, but none that should take you too long to browse. There are shuttles that constantly go between the visitor center and the Alishan Hotel if you are staying there. There is Alishan coffee, tea, and mochi you can try. Many of the restaurant serve hot pot as well if you need a meal-there is a 50s cafe within the park that's open 11am till late as well for a break.