The Garabogazköl Aylagy, alternatively the Kara-Bogaz-Gol (Turkmen: black strait lake) is a shallow inundated depression in the northwestern corner of Turkmenistan. It forms a lagoon of the Caspian Sea with a surface area of about 18,000 km² (6,900 sq mi). It is separated from the Caspian Sea proper, which lies immediately to the west, by a narrow, rocky ridge having a very narrow opening in the rock through which the Caspian waters flow, cascading down into Garabogazköl (whence the name of the bay – "Mighty Strait Lake" in the Turkmen language – comes).