Over four seasons, Iolo Williams goes to his favourite locations in Snowdonia to look for stunning wildlife, and meets people who help him discover the national park's true nature.

In this episode, it is autumn and Iolo takes us to hidden wildernesses with outstanding views of the season's colours and the big mountains of Snowdonia. On the lower slopes of the Carneddau range, red squirrels have returned to the national park after disappearing some 40 years ago. Below the magnificent Aber Falls, with its 37-metre drop from the high peaks, jays collect acorns in an ancient woodland.

Iolo finds fascinating old sheepfolds and Wales's native black cattle breed on the high slopes - both relics of a time when many more people lived and worked on the uplands and evidence of Snowdonia's changing nature. However, some things remain the same - wild goats rut on the Rhinog Mountains, a tawny owl and bats take up residence in an old church near Dolgellau and, in a nearby wood, dormice fatten up for hibernation. Also, the first whooper swans arrive back from Iceland to a lake below Snowdon - a sure sign that winter is on its way. Show less