A few weeks ago, I was walking through the Dongmyo Flea Market and was startled to see Dongmyo, the shrine itself to be open. We wondered in to take some photos.
The Dongmyo, or by it's full name Donggwanwangmyo, was built to honor the Chinese general Guan Yu. One of two such shrines built in Seoul, the other called Gwanwangmyo If it seems strange that a shrine in Korea would be dedicated to a Chinese general, you need to remember that Korea was a tributary nation to China for centuries. It was built after the Ming dynasty assisted Korea to defend themselves against Japan in the Imjin war. It's not so much that Koreans really honor this guy, but it was probably more to just placate the Chinese at the time.
Here you can see the shrine area to Guan Yu. But, you can only see from the outside, you can't go in.
Dongmyo is a nice stop if you're in the area to check out the flea market. Probably not worth a trip on it's own as I mentioned in the flea market post.