I add this link because I found it quite interesting.
They built a burial mound in the front and a tombstone in the back.
Typically in East Asia, the body is placed under the burial mound, but here, symbolically, they created a false tomb.
And on the tombstone built in front of it, they didn’t write the names of the dead people, but “Tomb of the Railroaders” (meaning “railroad martyrs”).
Perhaps this is the case with our first example image.
Add a tomb that looks very similar.
Incidentally, North Korea’s mass graves, which are so extensive and sporadically scattered that it’s hard to pinpoint a specific area.(1 kilometer radius in a NW-SE direction from the marker.) - View on Google Maps