The most salty lake on the Crimean Peninsula, it is part of the Opuksky Nature Reserve. Formed in the crater of an extinct mud volcano, it is separated from the Black Sea by a narrow isthmus. The area of the lake is 5 sq km (about 4 km by 1.8 km), and its depth is about 1.2 m. The pink colour of the water is due to the microalgae emitting red pigments of beta-carotene and iodine during photosynthesis, giving the lake's salt useful properties. Its water and mud are used in the treatment of joints and skin diseases.