Spring of the Mlava is located in the town of Zagubica, just at the northern foot of Mt. Beljanica, and is actually a small lake from which the river springs. It is inside a natural amphitheatre, open to the west with a small valley through which the water flows away. The lake is only about 30 meters wide and, due to its great depth, the colour of the water is dark green. Diving crews have managed to dive as deep as 70 meters, but they haven’t reached the bottom, so the depth of this lake remains unknown to this day.