The Caspian Sea is about 1,200 kilometres long from north to south — roughly the same as flying from London to Rome. Five countries share its shores: Kazakhstan, Russia, Azerbaijan, Iran, and Turkmenistan. The water is salty, but not as salty as the ocean.
Hundreds of species of fish live in the Caspian, including the beluga sturgeon — one of the world's largest freshwater fish, which can grow longer than a car. The Caspian seal, found nowhere else on Earth, basks on floating ice in winter and swims through the waters in summer.
Kazakhstan's Caspian coast has long sandy beaches, and the town of Aktau is a popular seaside destination where Kazakhs come to swim and enjoy the sunshine. The sea's northern part, close to Kazakhstan, is quite shallow and warms up nicely in summer.
Even though the Caspian is technically a lake, it behaves like a sea in many ways — it has its own weather patterns, its own currents, and even its own waves. Scientists sometimes call it an 'endorheic basin', which simply means water flows in (from rivers) but has no way out except by evaporation.