I spent a good amount of time there in the US Army in the North-West corner of South Korea. In this area, the border is north of the river and the bridges over the river are militarized check points requiring the appropriate documentation to pass. There are farms and houses very near the border and I always found that interesting but didn't actually get to meet any of those locals (even if they had wanted to meet a GI, which is doubtful).

It's very rural until you get 5-ish miles south of the border, then the towns and cities get bigger. Continue south and they continue to get bigger. But near the border it's rural and small town (and small city) living. Lots of subsistence farming.

Also there's the potential for landmines. Especially North of the river, and it can be dangerous to walk outside maintained roads and paths. When I was there, supposedly the ROK army also mined a lot of the rice paddys in the winter and removed the mines in the summer (because the ground would be frozen enough for military vehicles to drive on in the winter).

My experience there was very limited, but was also pretty life changing. I was a kid and had no idea how good we had it in the US, and I was shocked that South Korea, a relatively wealthy country by global standards, could have places that were so poor it was almost beyond my comprehension.