100 years ago the retreating Shakleton/Whataroa glacier left a 1k lake behind what had been the glacier's terminal morraine. Tucked in the deep southerly shade of the Butler range it gets little sunshine and even less in winter. Ice forms easily, frost lines the rocks, avalanches pour debris onto the ice, and sunshine on the far away peaks at the head of the valley reflects faintly off the surface.
If you're heading further on the lake can be skirted at lake level either side with out any real problem. In winter it is usually safer on the true left - but of course either side can be threatened by snow slides from way above.
A special place to linger and enjoy.
And its an easy 2 hours from the comforts of Top Butler hut.