Great Salt Plains State Park

"Oklahoma’s Great Salt Plains stretch for 11,000 acres, the evaporated remnants of an inland sea. The white, flat land shimmers in the heat, and a saline aquifer replenishes the sediment and contributes to the Great Salt Plains Lake, where catfish, sand bass, and other shallow-water fish thrive. Feel the salt crunch under your feet as you cross the plains, and maybe even bring home a souvenir. This is the only place in the world where you can dig for hourglass selenite, a fragile form of gypsum."