Si Nan National Park covers an area of approximately 583,750 rai or 934 square kilometres in Wiang Sa, Na oi and Na Muen districts. The undulating mountain ranges line up from the north to the south, paralleling on both the western and eastern sides. They divide the area into the west and the east. Along the riverside are mixed deciduous and deciduous dipterocarp forests. Within the compound of the ranges, there are hill evergreen forest, dried evergreen forest and pine forest. Rare animals that can be found are many flocks of peacocks, leopards, panthers, bears, deer, wolves and Asiatic wild dogs. Moreover, many important wild animals are wild elephants, bantengs, and gaurs, which usually migrate in and out the frontier between Thailand and the Lao People’s Democratic Republic. 

Interesting Attractions in the National Park are as follows:
Pha Chu’s foot is where the Office of the National Park is located. In winter, the sea of fog can be admired from the top of the cliff. When the fog is disappearing, the Nan River curving at the end of the forest can be seen. It is also a spot to view the sunrise. The distance to the spot is approximately 2 kilometres. The way near the summit is full of pointed rocks; therefore, a pair of sneakers should be prepared for the convenience of climbing. It takes 1 hour for a round trip. Those interested in climbing up to the summit of the cliff have to contact the park official. 

According to legend, Chao Ueang Phueng, the lover of Chao Chan Pha had to get married to Chao Chuang, making Chao Ueang Phueng upset for not being able to marry the man she loved. Therefore, she decided to commit suicide by jumping off the cliff. Chao Chan Pha later followed her and found out about her death. Chao Chan Pha; therefore, killed himself by jumping off the cliff as well. The bodies of Chao Chan Pha and Chao Ueang Phueng were next to each other. At the same time, Chao Chuang saw the woman he loved jumping off the cliff. He was very sad and decided to follow her as well. However, his body hurtled away. With the true love between Chao Ueang Phueng and Chao Chan Pha, in the next life, Chao Ueang Phueng was born as an orchid hanging under the Chan Pha Tree - Dracaena loureiri Gagnep., while Chao Chuang was born into a pine tree at the spot of his death. (Chuang in northern dialect means a pine tree, while “Ueang Phueng” refers to an orchid). This cliff has, thus, been called “Pha Chu”- the lovers’ cliff - since then.