Jung Yi-hyun (Yoon Hyun-min) and Kim Geum (Seo Ji-hoon) stumble across Seon Ok-nam (Ko Du-shim/Moon Chae-won) taking a bath at the Fairy Waterfall in episode 1 of Mama Fairy and the Woodcutter/Gyeryong Fairy Tale/Tale of Fairy (계룡선녀전) (tvN, 2018). The human duo are discovered when Kim Geum slips on a rock, and Ok-nam whacks them with a neck slice, making them fall unconscious.
In episode 13/14, Ok-nam comes here for a bath after returning to Gyeryong from Seoul, and she sees Kim Geum taking a bath himself. He spots her after he emerges from the water, and receives a warm embrace from her as they reunite. This is also where the fiery showdown between Yi-hyun (as Izy/Lee Ji/거문성) and Kim Geum (as Bausae/파군성) takes place in episode 14/15.
Gapyeong Yongchu Waterfall [가평 용추폭포] is located in Yongchu Valley [용추계곡] in the village of Seungan-ri [승안리] in the Gapyeong Township [Gapyeong-eup/가평읍], Gapyeong, Gyeonggi-do. Cheongsu Bridge [청수교] and Seasoning Days Pension Gapyeong [시즈닝 가평] can also be found a little further down north from here, if continuing down the road.
Seungan-ri, Gapyeong-eup, Gapyeong-gun, Gyeonggi-do
경기도 가평군 가평읍 승안리
Geolocation: 37.855003, 127.481288
Gapyeong Station [가평역], Gyeongchun Line
(Best to take a bus/taxi from here)
— submitted by Mich KDL