The Caspian Sea is one of the world’s natural wonders. It shares the characteristics of both a sea and a lake. In the past it was called a sea because of its great size and salty water. However, the Caspian Sea is listed as the largest lake in the world. There are about 130 rivers which bring their water to the Caspian Sea. But it is not a freshwater lake – its water is very salty. The Caspian Sea is famous for its wildlife. More than 850 kinds of animals and 500 different plants can be found in this unique sea. The Caspian Sea region is also one of the oldest oil-producing areas in the world. It is also rich in other natural resources.