Maisan (meaning "horse ears mountain") is a fantastical provincial park in Jeollabuk-do (province), about an hour from the provincial capital of Jeonju and about 3.5 hours from Seoul. The namesake peaks do resemble horse ears from a distance. Up close, it's a crazy conglomerate of pebble-to-basketball size rocks improbably held together. Despite the great cleaning efforts of the developers, a helmet is highly recommended.
There are two main crags-- Albawi, with moderate 1-3 pitch climbs (5.8 to 5.10) and Opera House, a steep amphitheater with routes from 5.10 to 5.14. An adjacent annex is being developed which promises more dramatic routes.
A couple of busses a day leave from Seoul's Nambu Terminal. Several a day from Jeonju Inner-city Terminal to Jinan. You can see the park from there, and it's a 30 minute walk or quick taxi ride. By road, there's a Maisan exit for Expressway 20, between Jeonju and the intersection with Expressway 35. Driving or cabbing, head around to the "small entrance" (on county road 30) or you'll carry your gear over the touristy pass. (From the small entrance, you'll miss some of the coolest temples/pagodas in the country. It is worth running past the turnoff on the main road 15 minutes are so for a look before or after climbing.)
Heading into the park from the small entrance you'll follow the main road past a lake on your left (with swan boats for rent) and the campgrounds on your right. Just beyond the lake a marked hiking trail heads off left. The approach for OH starts just behind this. The turnoff for Albawi is a bit hidden. Follow the trail into the woods; there will be a small trail to the right just after a small footbridge...don't take it! Hike on another .5k and look for another trail on your right. It will immediately go up a small ridge and continue to the crag.
All of Maisan Provincial Park was declared off-limits to climbing. The local government voted to close the park, including Al bawi, Opera house and even Yisan Myo, prohibiting bolts. Most, if not all, gear has been removed from Opera House:-(