The Caspian Sea is a large saltwater lake located between Europe and Asia, it is the largest lake by surface area in the world, with an area of 143,000 square miles (371,000 square kilometers). The sea is bordered by five countries, including Russia, Kazakhstan, Turkmenistan, Iran, and Azerbaijan. The depth of the Caspian Sea varies, with the northern and eastern parts being shallower than the southern part, which reaches depths of up to 3,363 feet (1,025 meters). The sea is an important source of oil and natural gas, and it is also home to various species of sturgeon, which are valued for their caviar. Despite being called a sea, the Caspian Sea is not connected to any ocean, and its water is not saline enough to qualify as true seawater.