Llyn Padarn is the result of millions of years of Earth movement and volcanic eruption, combined with an ice age. It is a glacial lake, dammed by a moraine and fed by the River Seiont, which is the same river that reaches the sea at Caernarfon, around 10 miles downstream.
The llyn is approximately 2 miles long and has a narrow gauge, railway running down the length of the north shore, with trains pulled by steam engines rescued from the nearby Dinorwic Slate Quarries.
We didn't ride on the train, but we waved at passengers as we were busy kayaking on the lake.
We hired them from here. It was really good value and we had the range of the whole lake :)