Sandstone balls up to twenty feet across, scattered over ground about the size of two football fields on a hillside south of Minneapolis. The sand was laid down along the edge of a sea that covered western Kansas about a hundred million years ago; groundwater later left a limy cement in some patches, the loose sand around them weathered off, and the cemented spheres stayed behind. Look for the angled lines of cross-bedding inside them, left by the currents that shaped that old shore. A local non-profit runs the park and the small admission keeps it open. PUBLIC, Ottawa County.
Sandstone concretions
Other places on the map within a couple of hours.
