The Aral Sea was a large salt-water lake, straddling the modern countries of Kazakhstan and Uzbekistan. It was fed predominantly by two rivers - the Syr Darya in the north, flowing through Kyrgyzstan, Uzbekistan and Kazakhstan, and the Amu Darya in the south, flowing through Tajikistan, Afghanistan and Uzbekistan. In 1960, it was the fourth-largest lake in the world, but the Soviet Union had a policy of diverting nearly all of the water from the Syr Darya and Amu Darya to irrigation channels to grow rice and cotton. As a result, the Aral Sea has almost entirely disappeared, splitting into two small, separate lakes which, in 2005-8, had a combined water volume approx. 10% of the former Aral Sea.
The Aral Sea is also sometimes considered an inland sea, because it was formed by the retreat of a much larger sea at the beginning of the Holocene.
The Kazakh novel The Dead Wander in the Desert looks pretty closely at the impact of the sea’s loss on the local people. It’s depressing, but a really moving book.