Once you've climbed 1085m, whether by foot or train, to reach the summit of Snowdon, the last things you'd expect to find are sea shells. However, some of the rocks along the railway track and surrounding the trig point contain fossil shells called brachiopods.

In the Ordovician period, some 450 million years ago, Snowdon was lying under a semi-tropical sea. Marine animals were abundant, including brachiopods which lived attached to or buried in the sea floor.

Volcanic activity was rife at that time, and Rhobell Fawr to the south, and probably another volcano to the north, were belting out hot ash which killed and buried these brachipods. Over time they accumulated and fossilised in volcanic rocks which were subsequently uplifted as continents collided, creating the mountains of Snowdonia.

If you're visiting in the summer months, look out for the rare Snowdon Lily which is only found in this national park. In February you may see the Purple Saxifrage blossoming through the snow. These arctic-alpine species are designed for life in extremely cold conditions.