The Dead Sea (which is actually a lake, not a sea) lies half in Israel, half in Jordan. It is 76 km (47 miles) from north to south and less than 16 km (10 miles) across. At 411 m (1,348 ft) below sea level, it is also the lowest point on earth. The water is so mineral-laden that it is around 26% solid. The therapeutic qualities of the water and its mud have been touted since ancient times, and spas are dotted along its shores. However, the Dead Sea is endangered. Its water level has gone down 12 m (40 ft) since the beginning of the 20th century because its main source, the Jordan River, has been over-exploited for irrigation purposes.