A few yards into the woods, here's the first hint that the area beyond this fence is not just a normal wooded hillside.

This is a concealed lookout post, set into the ground. A soldier would hide in this lookout and peer out through a narrow slit at ground level to watch for craft approaching from the west.

The viewing slit, beneath the concrete disk, is hard to see through the foliage in this photograph - I had to aim and shoot in the dark, so as not to draw attention from cars on the nearby road.