Hwaamdonggul Cave 화암동굴

photos by visitkorea.com

[Bus]
1. Take a bus from East Seoul Terminal to Jeongseon. Nine rounds of bus services are provided each day between 07:10 and 18:55, and the ride takes about 3 and a half hours.
Or,
Take a bus from East Seoul Terminal to Gohan. Twenty four rounds of bus services are provided each day between 06:00 and 23:00 and the ride takes about 2 hours and 50 minutes. (+82-33-563-9265). 
Then from Gohan you can travel to Jeongseon by bus that operates 10 times a day between 07:20 and 17:50. (+82-33-591-2860). 

2. Once in Jeongseon, take a city bus to Dong-myeon. 
Thirteen rounds of bus services are provided each day between 06:00 and 20:00 and the ride takes about 25 minutes.