The highest concentration of salt on Earth can be found in various salt formations or bodies of water. The Dead Sea, located between Jordan and Israel, is known for having one of the highest concentrations of salt in any body of water on the planet. The water in the Dead Sea is extremely saline, with salt concentrations averaging around 34.2%. This high salt concentration is primarily due to the continuous influx of water from the Jordan River and the extremely high evaporation rate in the region, which causes the water to become increasingly concentrated with dissolved salts.
It's worth noting that there may be other highly saline environments or salt formations that exist in different parts of the world. However, the Dead Sea is widely recognized as one of the most prominent examples of a natural body of water with an exceptionally high salt concentration.