The Blue Lake sits in the flooded levels of Dinorwig slate quarry above Llanberis, and the water is a shade of turquoise that seems impossible for Wales — the colour comes from fine slate sediment suspended in the water, and the surrounding quarry landscape of stacked slate shelves and rusted machinery gives it a setting no designer would have imagined.
Important: access to parts of the quarry is restricted and some routes have been closed by the landowner. This is not a formal visitor attraction — visit cautiously, stick to accessible paths, don't go alone, and check current conditions before travelling. At dawn or early morning, it is one of the more extraordinary places in Snowdonia.