Satellite image of the Mongolian salt lake Uvs Nuur. As you can see, the lake is at the bottom of a bowl-shaped section of desert surrounded by mountains, so no rivers flow out of it. Water can only escape by evaporation, leaving salt behind, so the water is pretty salty - about half as salty as the ocean.
There are fish in the lake, but I have no idea how they got there, since it isn’t connected to any other water in the world.














