Parts of the original city wall are still standing, but much of it has been either lost to history or eaten up by the modern-day buildings that shape Seoul's unique skyline. This particular gate is a restored version of the original structure.
Dorasan Train Station
It doesn't matter which site you visit in the DMZ, the ROK (Republic of Korea) soldiers are never far off. They make it abundantly clear where you are and aren't allowed to wander.