This makes me think about mining. 

In Australia, opal mining happens in a fairly primitive way. The opals are formed when silicate rocks are subjected to high-temperature water as the water snakes its way through deep-underground faults. The opals are then found stretched over a wide area, as nodes in a spidery network of rock faults. This means they have to be mined with a scattershot method. 

What usually happens is that a prospector hooks an enormous auger to the back of a truck and drives it out to the middle of nowhere. He anchors the truck with hydraulic lifts and drills the spiral bit of the auger into the Earth. He sifts the hill of dirt and broken rocks that the augur forces up out of the shaft it bores. And he either finds opals or he doesn’t. This type of mining has turned vast areas of opal-bearing land into swiss cheese. Full of vertical graves ninety feet deep and just wide enough to ensure you go all the way down. It has become a landscape where it’s suicide to walk around at night.

Rock salt is mined in a very different way. Geologic salt is usually laid down when an ancient sea dries up. And the salt flat it leaves behind is first buried, then folded into a corrugated sheet as it is compressed and distorted by the weight of rock above it. This tends to produce huge volumes of nearly pure salt. These volumes can be equivalent to a cube of salt, a half-mile on each side, just buried in the Earth. 

Formations like these tend to be mined in a way that turns them into architecture. That is, the salt tends to be so extensive and so deeply buried that the only way of excavating it is to make a kind of subterranean building whose only structural material is rock salt. Salt pillars, salt arches, salt hallways and salt galleries. The miners getting what they want from the formation—by necessity—creates something else: a vast and secret building, hidden underground and given definition by what has been drilled out of it. 

So you can be out there drilling dry well after dry well, flagrant in your destruction of an entire landscape. All in search of a fourth rate gemstone. 

Or you can be otherwise. And realize that beneath even the most featureless Kansan field, a secret city can be excavated. Vast, unified and private. Far too majestic ever to be confused with a grave.