The book is dedicated to the Orda underwater cave - the longest in Russia, the second longest in Eurasia and the longest in the world in gypsum. An idea of ​ ​ the karst processes that formed the cave is given, the patterns of karst development in the cave area are considered. Characteristics of geological, hydrogeological and geochemical conditions of the cave area are given. Information about its mineralogy is provided. For the first time, a description of the underwater part of the cave is given. Vegetation of the supragranular territory is described, including the Red Book species. The need to create a specially protected natural area in the area of ​ ​ the cave is justified.