The lake Ringedalsvatnet 700 metres below Trolltunga is man-made. Or rather, the water level is. It was a natural lake, but between 1910 and 1918 a 521-metre-wide dam was built across the valley, raising the water by over 30 metres. The dam is dressed in hand-cut granite and crowned with battlements like a medieval castle.
This reservoir feeds the Tyssedal power station. The construction changed the valley forever. Two of Norway's most famous waterfalls once thundered into this lake: Ringedalsfossen at 420 metres total height, and Tyssestrengene at over 300 metres of freefall. Both were major tourist attractions in the early 1900s. Today their water flows through tunnels instead.
From Trolltunga you look down at quiet blue water surrounded by steep cliffs. Beautiful, but a very different landscape from what Victorian tourists came to see.