Optimisticheskaya ("The Optimistic Cave") exceeds 130 miles in length, with more passage still being pushed. It features a brutal fractured grid as the entrance series; many turns greater than 90 degrees mean voice and light contact can be lost in an instant. The cave contains gypsum crystals of increasing size as one works further and further from the entrance. Our guides for this day trip, Igor and his nephew Eugene, nearly run through the cave knowing there is so much ground to cover.

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Igor and his nephew Eugene were our guides	Chris eyes a creamy gypsum formation	Chris takes a well-deserved nap at an underground camp	Lena checks out some gypsum flowers
Rebecca inspects a milky-looking gypsum deposit on the wall	Rebecca poses with a mud sculpture	Vitaly prepares for one of the cave's many climbdowns