Crystal Cave via Heineman Winery
Nicknamed the World's Largest Geode, the Crystal Cave's interior walls are covered in a crystals of bluish celestite. These fragile formations were created during the Pleistocene era - so basically about 2 million up to 11,000 years ago. The spectral color of the crystals is a bright magenta thus they were mined for fireworks. Thankfully Gustav Heineman had the foresight to halt the mining and turn this wonderful piece of natural history into a tourist attraction which helped the winery stay solvent through the Prohibition era. May through October you can tour the caves and drink wine - what better combination can you think of?