Alabaster Caverns State Park, OK
Alabaster Caverns State Park, the largest gypsum cave in the world open to the public, is 3/4 miles long. Its rock and mineral formations can be seen in few other places. Massive boulders of alabaster, a fine-grained mass gypsum, is seen in many colors: pink, white and even a rare black.
Nature created the underground site 200 million years ago when the area was covered by an inland sea. A perennial stream flowing through the cave is fed by various lateral tunnels and seepage from the roof. What is now a tiny brook, was once a roaring river and you can still see the evidence in the sculptured gypsum formations.