The coldest river in the world is most commonly cited as the Neretva, which flows through Bosnia and Herzegovina and into Croatia. The river, also known as the Narenta, makes up part of the larger Adriatic Basin region and empties into the Adriatic Sea. The river's basin covers a total area of 4,010 square miles.
The Neretva begins in the mountains of the Dinaric Alps at 4,026 feet above sea level, where it is formed by the runoff of three large glaciers and by an underground spring situated below the Jabuka Mountain.
This high elevation contributes to its extremely cold temperatures, which average just above the freezing point. The cold temperatures of the river are concentrated in the Upper Neretva.
The Neretva runs a course of 140 miles, 129 miles of which flows through Bosnia and Herzegovina, over a base of limestone and dolomite rock that forms a system of caves and sinkholes. This geological feature means that the Neretva is considered a karst river and is the longest of its kind to flow through the eastern part of the Adriatic Basin. The river is remarkable for its clean, pure water and its deep greenish-blue color.
According to worldatlas