In 1960, the Aral Sea was about the size of Ireland. It was full of fish, and around its shores were busy towns where families made their living from fishing. The lake gave them food, jobs and even cooler weather - a big lake helps keep the air around it gentle.
Two big rivers, the Amu Darya and the Syr Darya, used to flow into the lake from the mountains. From the 1960s onwards, more and more of that river water was used to grow cotton in the desert. That left less for the lake, and slowly, year by year, the Aral Sea got smaller. By 2010, it was less than a tenth of its original size.
On the dry lake bed, old fishing boats now sit on sand instead of water. People sometimes call this place a 'ship graveyard'. It is a powerful reminder that even very big lakes need looking after. Scientists and farmers around the world come here to learn.
There is good news too. The northern part of the lake, in neighbouring Kazakhstan, has slowly started to come back since a new dam was built in 2005. In Uzbekistan, people are planting saxaul - a tough little desert tree - across the old lake bed to stop the dust blowing away. It is patient work, but the area is healing.