Dream - Hidden areas under the ground covered with a layer of hard dirt

I've had dreams over the years of hidden areas under the ground covered with a layer of hard dirt, no more than a few inches thick in places, with big chunks coming off and falling in. Sometimes, depending on the dream, the areas are big enough to stand in, but sometimes they're only a few feet deep, and sometimes, at least in places, they're only a few inches deep, or even less.

In real life, I saw when voting in the presidential primary at a new place in January or February 2008, that at the side of the building was a long dip in the ground for runoff, and an area by it toward the building that was apparently opened up by the water, with a pipe coming from the building to some kind of box or enclosure with other lines coming and going. The whole area around it was opened up by the water with the sides of the hole sharply undercut into the surrounding land by some unknown but deep amount, eerily reminding me of my dreams.