Ondal Tourist Park [온달관광지] that includes a museum a cave and a fortress as well as a section which exhibits props used for filming has been the backdrop for a lot of historical K-Dramas. It lies around 4hrs by public transport south-east of Seoul.
Address: 23 Ondal-ro, Yeongchun-myeon, Danyang-gun, Chungcheongbuk-do
충북 단양군 영춘면 온달로 23
(영춘면 하리 147)
Geolocation: 37.062693, 128.492632