When you are walking from the Naejangsan National Park entrance area to the main park area, you should take the side path across the bridge of the stream running parallel to the main road. The side path will be surrounded by trees and you will be able to see some ginkgo trees (the leaves of the Ginkgo trees are used to make the popular health supplement Ginkgo Biloba which is good for blood circulation especially in the brain, and the nuts can be used to cook desserts). The reason why it is "Biloba" is because the leaves of this tree consist of two huge lobes (see photos). During peak of auumn season, the leaves will change from green to yellow colour.
There is a huge stream in Naejangsan National Park and you can actually see fishes and other aquatic life in them (because the water is so clear). One of the best places to spot the fishes is at the section of this stream from the Naejangsan tourist village to the park entrance (about 50 metres from the park entrance).
Because of the moist and dark forest areas in some parts of Naejangsan National Park, you will be able to see some interesting fungus growing (especially on dead logs) which come in all shapes and colours. It is important not to damage or eat these fungus because most of them are likely to be poisonous.
When you are at Naejangsan National Park visiting the various temples, you will come across the Sasa Borealis plant (a type of short bamboo) next to your trekking path. The seed of this plant can be cooked and used as a cereal by the local people (the seed is only produced at intervals of several years). Besides the Sasa Borealis, there is also a bamboo forest as you make your way up to Wonjeonam Temple.
If you take the leisure walk from the Naejangsan tourist village to the Donghak Revolution Memorial Park and Naejang Reservoir, you will pass by an area with many farms (along the river). In fact when you are taking the bus from Jeongeup to Naejangsan National Park, you will also pass by this farm area. This is a beautiful farmland area surrounded by rolling green mountains.
On the north of Naejangsan National Park is the Naejang Reservoir, one of the biggest reservoirs in the surrounding areas. When I was there in Oct 2007, there were plans to make this into a very nice water theme area (in fact construction was underway then). Next to this reservoir is the Donghak Revoulation Memorial Park as well as the northern entrance into Naejangsan National Park.
When you are walking from the Naejangsan tourist village towards the park entrance, you will pass by this huge building shown in the photo, which is I think the former Naejangsan Tourist Hotel (or is it under renovation?)
When I was planning to visit Naejangsan National Park, I actually wanted to stay here but is unable to communicate with them. Now I know it is probably because the hotel has closed down (?)