College Valley, Northumberland

The College Valley near Wooler, is one of the most remote, spectacular and wild glens in England. Running up from Hethpool village - where Admiral Collingwood, hero of Trafalgar, planted oak trees - into the Cheviot Hills, the valley culminates at around 2,000 feet, in a great chasm called Hen Hole, where towering black cliffs shield the College Burn from sunlight and even in midsummer you can still often find a small patch of snow, known as the Snow Egg.

Ravens and peregrine falcons nest in the cliffs, wild Cheviot goats and roe deer stalk the heather-covered tops and in autumn, salmon and sea trout leap up the rocky gorge of the Hethpool Linn to their spawning grounds. Add in bronze age hillforts, stone circles, burial cairns and barrows, and an ancient legend of shepherds lured to their doom by mysterious music, and there's little wonder Sir Walter Scott - a visitor in 1791 - made this the lair of romantic outlaw Black Adam of Cheviot.

You can access it by foot from Hethpool, but anybody wanting to drive up the glen from the village must first buy a permit. Only 12 permits are issued per day, they cost £10 and can be obtained solely from Sale & Partner, Glendale Road, Wooler.
• 01668 281611; college-valley.co.uk
Harry Pearson

Falling Foss, North Yorkshire

Littlebeck is hidden away in the Esk Valley, a valley so steep and lush that it might be in the tropics rather than three miles from the North Yorkshire coast. Footpaths wind down from the valley top, or you can hike up from Littlebeck hamlet past overgrown quarry workings and mysterious pools. An enormous scooped-out boulder is carved with "The Hermitage" and "GC", for George Chubb, the Littlebeck schoolmaster who had it built as a fancy in 1754. Seats inside the cave and on its rock roof are comfy for listening to nearby Falling Foss waterfall splashing away. A bewitching place.
• OS map ref: NZ 886035
Martin Wainwright

Sgwd Y Eira, Wales

There is something magical about climbing behind a waterfall, watching as the curtain of water cascades from the rocks above. On the south fringes of Brecon Beacons national park, a natural path leads behind the waterfall Sgwd Y Eira (the waterfall of snow), and has been secured so everyone can enjoy the magic. It's the only one of four waterfalls enclosed in Coed y Rhaeadr, the "wood of the waterfalls", that you can walk behind.
• Walk from the car park at Cwm Porth; breconbeacons.org
Carlene Thomas-Bailey

Carsaig, Isle of Mull

Near the village of the same name, Carsaig waterfall has a cave behind it from which you can see through the spray to the hilly Isle of Jura.
• From Iona, follow the road to Carsaig and its old pier where you'll find a car park. Follow the footpath east until you see the waterfall
CTB

Source of the Thames, Gloucestershire

The real source of the Thames is a bone of contention, with at least three places claiming that status. The official source can be found via a delightful walk from the stone Cotswolds town of Cricklade, Gloucestershire. The Thames Path runs via the lakes of the Cotswold Water Park, and passes the settlements of Ashton Keynes, Somerford Keynes, Ewen and Kemble, criss-crossing the young river. Look out for a marker that reads: "This stone was placed here to mark the source of the river Thames."
thames-path.org.uk
OS map ref: SU 067938
Oliver Bennett

Source of the Severn, Wales

The river Severn's source is in a wild, wuthering spot in the Welsh hills. Starting at the picnic area and car park at Rhyd-y-benwch in Hafren Forest, an orientation board shows the walk's route, which follows wet ditches and boggy banks through the forest before arriving at the Severn's official source, a pool marked by a wooden post, 620 metres high.
• Llanidloes, the nearest town, is just off the A470, between Newtown and Aberystwyth; severnway.com/walks
OS map ref: SN 857869
OB