is a small lake of glacial melting
on the southern side of the famous glacier Vatnajökull
The glacier tongue falls inside the lake, creating the icebergs you can see in the picture
It is close to the famous lake Jökulsárlón, the most popular place for iceberg boat tours. But ice is melting so fast that some company is starting also to propose tours in the Fjallsárlón, but is just a matter of time: sooner or later, no ice will be falling straight in the water; fiords will replace glaciers in this area.