Boryeong is a west-coast city in South Chungcheong, best known for turning its tidal mud into one of Korea's rowdiest summer festivals. That sounds gimmicky, and in July it partly is, but the setting helps: Daecheon Beach is a long, open stretch of sand facing the Yellow Sea, with ferries and islands just offshore.
The city is more spread out than its beach reputation suggests. Inland, Seongju Mountain holds old coal-mining history, forest drives, and the remains of Seongjusa, a Baekje-era temple site that later became important to Korean Seon Buddhism. North of town, the old Chungcheong naval fortress looks out over the coast and the islands.
Boryeong works best as a beach-and-sights day from Seoul, Daejeon, or Gunsan, or as an overnight stop if the Mud Festival is on. Outside summer it is quieter, but the mix of Daecheon Beach, Wonsando, and the inland historic sites still gives a traveler enough to do.