Iolo Williams explores the magic of the Brecon Beacons over the seasons in this stunning new series. He braves a blizzard on the high peaks, yet the lowlands can still be sunny. On the snowy slopes, foxes look for food, while a great grey shrike, a ruthless hunter from Scandinavia, looks for animals to eat. Cormorants congregate to fish on reservoirs, some birds are already breeding on the River Usk and red deer hide away in secluded gullies in one of the wildest locations in the Beacons. It's a magnificent diverse landscape with huge caves, stunning waterfalls, ancient woodland and canals.

It's spring and the nesting season is in full swing. While hundreds of dotterel are taking a rest on the Black Mountains during their journey from Africa to their breeding sites in Scotland, peregrines are already nesting in an old quarry in the central Beacons. Next to the largest natural lake in south Wales, water voles are managing their ditches. Iolo Williams explores the most crooked church in Britain and an old gunpowder works and finds that a 300-year-old stone wall reveals the history of this magnificent landscape.

It's the busy summer season. A fox family is playing below the Carmarthen Fans, lizards bask in the sun on limestone pavements in the upper Swansea valley and hundreds of dragonflies emerge from pools in the uplands near Brecon. Iolo Williams is on the Black Mountain foothills as sheep are gathered by shepherds on horseback and a group of dedicated volunteers are trying to repair a mountain. Ancient botanical cures for ailments and old steam railways are two of many hidden histories.

Autumn is the season when the landscape is at its most colourful. Iolo Williams finds himself in the midst of a flock of thousands of fieldfares arriving from Europe to escape the colder continent. They gorge themselves on berries in trees surrounding the smallest church in Wales. In the Usk Valley, bats feed before they hibernate in caves, and migrating ducks gather on Talybont Reservoir, ready for winter. Underground, cave spiders are lurking, and sea trout are heading upstream to spawn in the rivers.