Hallasan is one of Korea's three most sacred mountains. It is on Jeju-do, the southernmost island of Republic of Korea. It is 1,950m tall. On the top of Hallasan, there is a crater called Baek Rok Dam. It was an active volcano until about 25,000 years ago. It is now dormant. Hallasan is made of basalt, a type of black rock that is produced by volcanoes. It extends east to west. The south side of Hallasan is very steep. The slope of the north side is gentle. The east and south are relatively high but smooth.
There are seven trails on Hallasan.
- Eorimok covers a total of 6.8km and takes about three hours for a one way trip.
- Yeongsil is a 3.7km foot trail from Yeongsil Resting Area to Witsae-oreum Shelter. A one-way trip takes 1 hour and 30 minutes.
- Seongpanak trail is a 9.6km course and it takes about four and half hours for a one-way hike.
- Gwaneumsa trail is 8.7km long and takes 5 hours for a one-way trip.
- Donnaeko trail covers 7 km and takes about 3 hours and 30 minutes for a one-way trip.
- Eoseungsaengak trail is 1.3km long and a one-way trip takes 30 minutes.
- The 1.5-kilometer Seokgulam Trail takes about 50 minutes one away to Seokgulam hermitage.
Hallasan has subtropical plants, warm-climate plants, and subarctic plants. In spring, there royal azalea, and yellow rape. There are also maple trees. In winter, the mountain is covered with snow. There are deer, which are the symbol of Hallasan.
The ever-changing colors of the scenery make people admire the beauty of nature, and this is why hallasan was selected as a national park on March 24 1970, and a UNESCO World Heritage Site in 2002. During the last week in January, there is a snow-flower festival in Hallasan.