They built it to keep the rabbits out, son.

We drive through a continuous basin between a pretty impressive set of
mountains. We've temporarily left the farm lands behind and, in spite
of the chill, it is clear we are getting closer to the desert.
The grass is a pale dusting of green over the yellow bones of the
earth. In the distance you can see proper shepherds surrounded by
fluffy white things that look far too sweet to be sheep.
The ancient remains of the great wall keep pace with us out the
northern windows of the truck. We have discussed what excellent cover
they'd make for a pee stop.