Seoraksan
At 1,708 meters (about 5,600 feet), Daecheongbong is Seoraksan's highest peak, and a favorite with novice mountaineers. Depending on where you begin your journey, the trek to the top can be done in as little as three hours. Lower down, the popular Cheonbuldong Valley explodes into a riot of color in fall. But the two-hour trek to the top of Ulsan Bawi (876 meters) can be particularly rewarding, not just for the physical exercise, but also the sensational views of the eastern sea, Daecheongbong and the valleys below.
Bukhansan
Seoul, amidst its urban sprawl, has seven mountains. But the greatest of these is perhaps Bukhansan, sometimes called the "lungs of Seoul" for the role it plays in helping clear out the city's CO2. The three-hour hike up to Baegundae, Seoul's highest peak (836 meters) beginning from the Bukhansanseong Hiking Support Center near Gupabal Station (subway line three), is one of the most popular trails.
Taebaeksan
Dangun, the legendary founder of Korea's ancient kingdom Goguryeo, was supposedly born on a mountain called Taebaeksan. On the 1,567-meter highest peak, Janggunbong, there's Cheonjedan, "altar for heavenly rites," where, in an earlier time, the devout would perform rites to honor the gods.Taebaeksan really blooms in the winter when the branches sparkle with frozen snow. In Korean, the sight is literally referred to as "snow flowers."
Fall here is, however, are sadly underrated. While less monochromatically striking, autumn weather makes for good walking, and Taebaeksan's leaves are also a-changing. Despite its height, the way up to Janggunbong is more of a gentle slope than a craggy scarp. Getting there should not take more than two hours from the Baekdansa (Baekdan Temple) entrance.
Songnisan
The most important thing to know about Songnisan is that it's a damn good-looking mountain. In autumn, the leaves die in varying shades of scarlet alongside the weird and wonderful rock formations that make up Songnisan's cliffs.
The highest peak is Cheonwangbong at 1,058 meters, but the loveliest is cloud-shrouded Munjangdae at 1,054 meters. The view from Munjangdae is also spectacular, and if you start at Shilla-era Buddhist temple Beopjusa, you can get there in three hours.
Jirisan
The granddaddy of South Korea's mainland mountains, Jirisan is huge. The park that encompasses the mountain's many peaks is South Korea's largest national park (484 square kilometers). The highest peak, Cheonwangbong (1,915 meters), is second only to Hallasan. But one of the best places to really get into the spirit of autumn is in the valleys, such as the spectacularly beautiful Piagol Valley to the south. You can begin at Yeongok Hiking Support Center and walk the entire length (five hours), or linger in place to gawk. The valleys change later than the peaks, so you can get fall color there a few weeks after the show is over at the top.
Naejangsan
On its own merits, it might seem like Naejangsan doesn't really have a place on a representative list of South Korean mountains. Sinseonbong, at a measly 763 meters, is its highest peak.But Naejangsan's yearly transformation is so radiant that it has been known has fall foliage central for about 500 years.
The most commonly traversed course is the three-hour walk to peak Seoraebong from the Hiking Information Center, but the show starts before that. On the walk from the Hiking Information Center to Buddhist temple Naejangsa you come across an avenue lined with 108 densely packed trees, decked out in all manner of golds, oranges and reds.
Hallasan
Hallasan, a volcanic mountain that makes up most of Jeju Island as well as South Korea's tallest peak (1,950 meters), is also more of a winter player. But that doesn't mean you can't appreciate its autumns (as well as the volcanic cones or lava flows that also decorate the landscape).
Many visitors start at Hallasan National Park's Visitors Center and make their way up along the Eorimok Trail, but this trail won't take you to the peak, where Baeknokdam, the crater lake at the top, awaits.
The Seongpanak Trail, which starts at Seongpanak, to the east, will take some patience -- five hours' worth -- to complete, but it takes you to the lake.