While visiting South Korea we booked an all day tour of the DMZ. Tours are available through the USO, but we did ours through Discover Seoul tours.
When told people we were going to Korea, almost everyone asked if we were going to North Korea. I always said no, but we ended up entering 10 feet into North Korea at the Joint Security Area in a conference room that spanned the dividing line between North and South Korea.
The tour also included a visit to a tunnel that the North Koreans had dug into South Korea. It was not very tall, so at 6 foot tall, I hit my head a few time. Good thing that we were all provide with a hard hat.
We did not make it out of the Seoul area. We did visit the museum and beach at Inchon. Small museum, but interesting. Nice day at the beach, but I was one of only a few people that took there shirt off at the beach.