The Moon Shin Museum is on the edge of Muhaksan and offers a great view of Masan and it's harbour. Along that edge of Muhaksan are (okay, were - I lived there twelve years ago) several old buildings that weren't quite decrepit and several small temples and shrines. Also, the hike up the mountain is good fun.
Yeongwol has everything except the ocean. It is a sort of adventure capital for Korea with rafting, climbing and might even have a paint gun area. It is also a dark-sky zone and has an observatory. Apparently, it also has eighteen museums.
I'd like to add to the article by suggesting that all travelers with a bit of time on their hands should ask about local museums. They are often kitchy, but almost always fun. Sadly, Sokcho's museum is well-done and in a modern building, but doesn't really have a special local identity. The whale museum in Donghae, in contrast, is fantastic.
Added Later: Joongang also has an article specifically about Yeongwol's museums:
The first museum to open was Yeongwol Book Museum, which opened in 1999 in what used to be a school. Although the locals criticized the developers for opening a museum deep in the mountains, Chosun Minwha Museum opened the following year. Museum after museum began to fill the empty buildings.
Area residents are still at a loss to explain why so many museums opened here. However, it is thanks to the museums that Yeongwol County was designated a special museum district last year, which has led other local governments in the area to try to repeat the phenomenon to open more museums.