The Sana is a big river by Dinaric standards — wide, cold, and clear enough in its upper reaches to sight-fish rising trout along the limestone edges above Ključ. Brown trout and grayling hold the fast water where the current shelves off the gravel bars; the hatches are seasonal but reliable, and the fish are as selective as the clarity of the water demands. Lower down, where the valley opens and the current slows through deeper bends, the hucho move in. They are large, secretive, and found by covering ground methodically rather than by luck. One of the great salmonid rivers of south-eastern Europe, and half the world doesn't know it exists.

• Limestone