About This Race
TransJeju by UTMB's 148K traces a demanding route around Jeju Island, a volcanic UNESCO World Heritage site off South Korea's southern coast. The course circles Hallasan, South Korea's highest peak at 1,950 meters, requiring runners to manage the island's dramatic ecological transitions from subtropical coastline through temperate forest zones. With approximately 7,000 meters of elevation gain, this distance serves as the series' signature challenge, drawing experienced ultra-runners to test themselves on technical volcanic terrain that contrasts sharply with typical mountain ultras. The route's character comes from Jeju's unique geology. Sections traverse hardened lava fields and volcanic rock, demanding careful foot placement and durability in both runner and equipment. Extended passages through forested trails and exposed ridgelines require runners to manage widely varying conditions within a single race. The October timing typically provides stable autumn weather, though wind exposure can be significant on higher, treeless sections. This is a race for runners with established 100-mile credentials who want to experience trail running in East Asia's distinctive volcanic landscape. The combination of technical footing, sustained elevation change, and the logistical challenge of a point-to-point island circumnavigation makes the 148K a genuine test of ultra-distance skill rather than a scenic tour.
The course circumnavigates Hallasan volcano, moving through multiple climate zones as runners gain and lose elevation repeatedly around the mountain's flanks. Volcanic rock sections require technical navigation, while forested passages offer brief respite before the next climb. Water and aid stations are positioned strategically, but runners should expect extended self-sufficient sections given the remote nature of portions of the route.
Location
Practical Info
Early October on Jeju typically brings mild temperatures in the 15-20°C range at lower elevations, though conditions vary significantly with altitude. Runners should prepare for wind exposure on ridgelines and potential rain, as autumn weather can shift quickly. Coastal sections may be warmer and more humid than higher elevations.
CJU - Jeju International Airport
Jeju City serves as the primary base, offering a full range of hotels and guesthouses. The island is accessible by frequent flights from Seoul and Busan, and English signage is common in tourist areas. Book accommodations well in advance, as the UTMB event draws international participants and coincides with autumn tourism season.
Best For
Notable Features
TransJeju offers access to Jeju Island's volcanic landscape, a UNESCO World Heritage site rarely featured in international ultra-running. The route's ecological diversity—from coastal subtropical zones to near-alpine environments—provides terrain variety uncommon in single races. As part of the UTMB World Series, the event attracts an international field while showcasing Korean trail running culture and Jeju's unique geology.