Based on the world record nomination from Europe Records Institute (EURI) and Decision No. WK/USA.INDIA/620/2020/No.76, World Records Union (WorldKings) officially declared Optymistychna Cave as World's longest gypsum cave.
Optymistychna is a gypsum cave located near the Ukrainian village of Korolivka, Borshchiv Raion, Ternopil Oblast. Approximately 230 km (140 mi) of passageways have been mapped within. As a result, it is the longest cave in Eurasia and the fifth-longest cave in the world and the longest gypsum cave in the world.
The cave complex was discovered by the speleologists of the Lviv speleological club "Cyclope" in 1966. It was entirely unknown before then. There have been more than 50 expeditions since then, but exploration has slowed significantly in recent years, and very little surveying is currently being done. In 2008, the cave was recognized as a Natural Wonder of Ukraine.
The entire cave lies under a 2 km square area in a layer of Neogene period gypsum that is less than 30 metres (98 ft) thick. The passages tend to be fairly small, no more than 3 metres (10 ft) wide and 1.5 metres (5 ft) tall for most, although at intersections they can be up to 10 metres (33 ft) tall.
They are often choked with mud. They comprise a dense network on several levels, making Optymistychna known as a "maze cave".
Optymistychna's gypsum bed is topped with a limestone layer, which has seeped through into the cave via erosion and formed into calcite speleothems. At other places, the gypsum has formed crystals, often tinted a multitude of colors by mineral salts. In some areas, large gypsum rosettes have formed, colored black by Manganese oxide.
According to en.wikipedia