The Elan Valley in Wales - Shelley took inspiration there. You can walk for miles and not see a soul or hear a jetski
With the first hint of rising mercury, columns of cars pour into Dartmoor, the Peaks and Lakes, all, ironically, in pursuit of an "unspoilt wilderness". Come August and most of the "wastes" that thrilled Boswell, Wordsworth and Hardy are gridlocked. The trouble is many of Britain's most beautiful landscapes are simply too well-known. In these crowded isles, it seems impossible to find an empty vista - but a spectacular wilderness does still exist.

The Elan Valley is the gem that inspired a young Percy Shelley - he fled there after he was sent down from Oxford for atheism - and Coleridge, yet today it is almost completely overlooked. Mention it to a friend, and the chances are that he or she will never have heard of it, let alone be able to find it on a map.

Nor are there many locals to clutter the views. Mid-Wales remains the most-sparsely-populated place south of the Scottish border, somewhere where one can walk, bike or ride all day in peace and solitude.

Forget struggling along well-worn paths to reach the crowded peaks of Snowdon or Sca Fell. Anyone walking to the 2,116ft summit of Drygarn Fawr would be unlucky to see anyone on the walk, and completely jinxed if they had to share the view at the top.

But the valley's most notable features are its lakes - the brainchild of Joseph Chamberlain (1836-1914), who turned Birmingham into "the best governed city in the world", and sired Neville Chamberlain - another lord mayor of Birmingham, whose name was later sullied by the notorious "peace in our time" compromise with Hitler just before the Second World War.

Chamberlain Senior and the Corporation of Birmingham wanted a reliable supply of clean water for the rapidly-growing city. Their answer was to buy a huge chunk of the Cambrian mountains, construct four dams along the Elan river as it cascaded down towards the Wye and build a 73-mile pipeline to the Midlands.

Today, the monstrous stone dams possess an austere beauty - much-loved by makers of car ads - that's lacking in their concrete counterparts. They're at their best after rain when they are cloaked white with a thundering torrent of cascading water - a rare case of industrialisation having clear environmental benefits, though at a high human cost.

A century ago some 400 people were evicted to ensure the purity of the water supply (three-quarters of them lived above the water line), and even today the owners impose rigid limits on the use of agricultural chemicals and enforce strict stocking limits on the handful of remaining farms.

Camping and water sports are also banned, and the result is that the valley has become a tranquil haven for many of Britain's rarest flora and fauna - so much so that 80 per cent of it is designated as a Site of Special Scientific Interest (SSSI).

At the top of the valley system there lies a vast plain of heather and tussock grass, scattered haphazardly with peat bogs. One of Britain's last great wildernesses, some 400 square miles is devoid of human habitation, and frequented only by merlins, golden plovers and grouse.

Further down, hanging oak forests cling to the slopes, home to pied flycatchers and crammed with rare mosses and fungi. As peregrines patrol the skies above, the numerous waterfalls and streams below have plenty of dippers and brown trout, and this is also a rare otter stronghold.

The area's most famous resident, however, is the red kite. Once reduced to barely a dozen birds, the numbers are now so high locally that it is hard to spend half an hour outdoors without a sighting of a magnificent forked tail and 5ft wingspan. Anyone who is a bit rusty on their identification skills should beat a path to the winter feeding station on the outskirts of Rhayader where anything up to 50 birds hang around the skies in the hope of a free meal. In spite of the water companies' past hostility to residents and the precious range of habitats, today the Elan Valley Trust welcomes tourists with an excellent visitor centre that includes displays, maps and local literature.

The rangers are helpful too, and run a range of organised nature walks and activities. More importantly, though, there is a right to roam policy for walkers, and no shortage of suggestions for those unfamiliar with the area.

Most visitors opt for a stroll along the banks of the reservoirs - none the less spectacular for their relatively forgiving gradients. More adventurous souls can retrace the "Monk's Trod", the ancient path which once linked the great Cistercian monasteries of Strata Florida on the west of the Cambrians with Abbey Cwm Hir to the east.

But the 20-odd miles between Rhayader and Tregaron are more suited perhaps to horse riders, who can wander both in and out of the valley as freely as walkers. It is also a great area for cyclists. Thanks to the long-defunct railways used to construct the dams, there are miles of relatively flat paths in the valley itself, with the Elan Trail (National Cycle Route Sustrans 81) winding over the hills to Aberystwyth. Nearby is Sustrans 8 that runs the length of the Wye Valley.

Meanwhile mountain bikers can head for the hills, either trusting to maps and compass, or using a local guide. Anglers will also feel at home, with permits - available at Rhayader newsagents - to catch the monster brown trout, rumoured to lurk in the reservoir depths. But they won't have much luck with the dwindling Wye salmon.

In the end, however, visitors are all drawn by one thing - the lack of company and the spectacular mix of environments. Barely two hours from the Midlands and four from London, the area is ripe for a long weekend.

The Rhayader Tourist Information Office (01597 810591) will provide local contacts, while the Elan Valley Hotel (pounds 30 per person per night, 01597 810448) is a small, friendly base which welcomes children and dogs. Or the plentiful B&Bs in town start at about pounds 15 per night, and there are also camp sites next to the Wye and at Cwmystwyth.

Bikes can be hired from Elan Cyclery (pounds 12 a day, 01597 811343) and horse riders can either bring their own mounts or hire them from Lion Royal Hotel (pounds 30 a day, 01597 810202)