There's a mysterious mound back of this house way out in the Sandhills of Nebraska, that the now-owner of the property (the ancient elderly gentleman who used to cut the grass here), and the guy who currently cuts the grass (and moves the snow), insists covers the septic tank.
It's obviously a man-inspired, rather than a natural occurrence, phenomenon; its peak is circa a little less than two feet above the surrounding ground, and the "bump" covers an area about 20' x 20'.
Grass grows lushly above it, but it's kind of a deeper-green sort of grass; also the texture of the soil appears sandy, as compared with the usual pure black dirt here.
Near as the now-owner of this property can recall, it was installed in "'38 or '39," and to his knowledge never cleaned out. He says it was made of concrete.
There exist no plumbing problems here, and being a single person enamoured of the spartan life, I don't generate a whole lot of waste. And the place was vacant from the late 1980s (1988 I think) until I came here in the autumn of 2005.
A few years ago, I dubbed the mound "the Atman."