A reservoir in a deep cwm under Elidir Fawr, a few miles north of Llanberis. It is the upper lake of the Dinorwig pumped-storage power station, whose turbines are hidden inside the mountain, but from the path it looks like any other high mountain lake. A loop from the Deiniolen side climbs to it and around it, and sees a fraction of the people on the Llanberis paths across the valley.
Marchlyn Mawr
High reservoir under Elidir Fawr, the top lake of the Dinorwig power station, on a quiet loop above Deiniolen
Most visitors miss this
My favourite walk (seriously, it's a stunner)