The Garabogazköl Aylagy or Kara-Bogaz-Gol (Turkmen: Garabogazköl, lit. ' black or dark strait lake') is a shallow water-filled depression in the northwestern corner of Turkmenistan. It forms a lagoon of the Caspian Sea and has a variable surface area, being about 18,000 km2 (6,900 sq mi). The Caspian Sea proper sits immediately to the west, mostly divorced by a narrow, rocky ridge having a very narrow opening through which the Caspian waters flow, overwhelmingly, into it. This prompts the Turkmen reading of gara as "mighty". There is likely to be a subterranean highly saline flow, if only when evaporation is less fierce in winter, as in the case of the Turkish Straits year-round. The lagoon's volume fluctuates seasonally, accentuated by its salt evaporation ponds and natural counter part s