The War Memorial of Korea, Seoul
I visited several museums in Korea, including the Folk Museum (Gyeongbokgung, Seoul), The National Museum of Korea (Seoul) and the Gyeongju National Museum. None touched me on an emotional level the way that The War Memorial did.
The museum had a large section dedicated to explaining the ongoing conflict with North Korea. A young Korean tour guide showed me, as part of a tour group, around this section of the museum and systematically explained the various stages of the War. The museum had artifacts dating back to 1953, photos and lists of the nations who backed S. Korea as China stepped in to back North Korea. Our tour guide highlighted the separation of families, divided and fighting each other on the two sides.
I highly recommend visiting the War Memorial, and timing it with an English tour group!