Jangbuljae is where every hiker will have to pass to reach the top of Mudeungsan. It is also where the colonnades of the summit can be viewed at a glance. Janbuljae features both steep cliffs and gentle slopes. Such characteristics are observed when water within rocks experience seasonal freezing and thawing processes under periglacial conditions. Since Jangbuljae is connected with the summit of Mudeungsan and Ipseokdae, the site is an important geosite as it provides information on how the area has evolved over the years. Furthermore, a large-scale silver grass colony creates a great spectacle. Jangbuljae is estimated to have formed around 50,000 to 60,000 years ago. Even though the site is also recorded as ‘Jangbulchi’ in Munheonbigo (a kind of encyclopedia) and ‘Jangbuldong’ in Donggukyeojiseungram fifty-five volume set of geography books published during Joseon Dynasty), it is referred to as Jangbuljae by the locals. Eun-sang Lee speculated during his trip to Mudeungsan that the former name of the site, ‘Janggoljae’(means a slope in a valley) was replaced by ‘Jangbulchi’ after Jangbul Temple was built. Donggukyeojiseungram and Yuseoseokrok (19 extant essays on Mudeungsan) suggest that iron ore was quarried at Jangbuljae.