Orda Cave (Ординская, Ordinskaya) is a gypsum crystal cave found underneath the western Ural Mountains. The mouth is near the shore of the Kungur River just outside Orda, Perm Krai in Russia. The cave system stretches over with around over the overall length being under water. This makes it one of the longest underwater caves and the largest underwater gypsum cave in the world. It contains the longest siphon in the former Soviet Union (935 meters).