Alabaster Caves is a park in Oklahoma State, home of the largest gypsum caves in the world. Entering through the entrance to the rock, you find yourself in spacious well-lit halls, 60 meters in diameter and 23 meters high. The walls are covered with a 50-cm layer of selenium-like glass-like crystals. But most of the formations are alabaster - white, pink and black. There are only two more black alabastres in the world - in Italy and China.