All that glistens is not gold ... it's sometimes blue!
Happened upon the place a few years ago, when the Quarry lake was accessible via a tunnel and people could swim in there. The tunnel was recently filled in and now you have to abseil down to sample the blue waters.
Thid hidden lake in Snowdonia National Park is guarded by towering crags and is remarkable due to its rich blue colour.
A narrow path skirts two sides of the lake at the foot the vertical cliffs. According to local rumours, the lake is deeper than its height above sea level.
You are looking for a glistening container hidden under a rocky ridge at ground level and covered by slate, of course.