Gardening: The sublime to the precipitous: Anna Pavord explores the narrow gulleys and vertiginous crossings at Hawkstone Park, the Alton Towers of its day

Nemesis, the new thrill ride at Alton Towers, the theme park in Staffordshire, was officially opened by the Gladiators this week. You may have seen the advertisements, promising whiter-than-white knuckles on this new roller- coaster, which has chairs hanging under the run, ski-lift fashion.

Almost within screaming distance, at Hawkstone Park in Shropshire, is the Alton Towers of the 18th century, a breathtaking circuit laid out between four bizarre outcrops of rock that rise dramatically from the flat land north of Shrewsbury. The Awful Precipice is Hawkstone's Nemesis, the Gloomy Grotto its ghost ride, Gingerbread Hall its burger bar.

At its peak, Hawkstone could also offer you a real, live hermit in a stone rubble hut thatched with heather. He had all the regulation props - the skull, the hour-glass, the book - and was, said an early visitor, 'tolerably conversant'.

So many visitors flocked to see the wonders of Hawkstone that its owner, Sir Richard Hill, built a hotel to accommodate them. Dr Johnson came with Mrs Thrale and found the place well up to scratch. 'The ideas which it forces upon the mind are the sublime, the dreadful and the vast,' he wrote. In a word (although Dr J never used one word where three would do), awesome.

The Hills, big spenders during the 18th and 19th centuries, came to the end of their loot in the 20th, and the estate was sold, split up and redeveloped. The Hills' house became a Redemptorist Pastoral Centre, and a golf course was laid out around the hotel. The hermit found other employment.

The wide carriage rides, planted in the 19th century with rhododendrons and pines, gradually closed in. Prisoners of war systematically picked the grottoes clean of their decorative shells and quartzes. The statue of Sir Rowland Hill (Sir Richard's father) tumbled from the top of the 100ft monument built to commemorate him.

Although visitors no longer made special journeys to see it, Hawkstone was not entirely forgotten. Local people still walked there. The Garden History Society worried about its future. English Heritage gave it Grade One status in its new Register of Historic Parks and Gardens. Then, rather miraculously, its owners decided to spend several million pounds on a full-scale restoration of Hawkstone's landscape.

Hawkstone Hall, the Hills' house, no longer forms part of the estate, but the core of the original layout is still intact, four huge eruptions of sandstone rock that plunge dizzyingly into gulleys and ravines below. On one plateau are the remains of Red Castle, built in the 13th century, when the Welsh, rather close here, were being more than usually troublesome.

Another vast outcrop, called the Elysian Hill, looks out over the Grand Valley to the biggest area of rocky sandstone, known as the Terrace, a three- quarter-mile stretch that leads on to Grotto Hill and the Awful Precipice.

The whole thing is a brilliant exercise in manipulating the senses. You feel your way along a passage in pitch darkness, then emerge at the mouth of a cave, organised just so as to catch the best view. You pick your way through an astonishing stone gulley, up steps hacked out of the solid stone floor, almost holding your breath for fear that the stone walls, higher than a house, are going to contract, squeezing you in a straitjacket of rock.

The new tour starts at a red sandstone building with Gothic arches called the Greenhouse. This is where Colonel Hill (Sir Richard's son) had his 30th birthday party in 1802, parading in front of the windows for his guests' entertainment the animals brought back from his campaign in Egypt.

There was a menagerie here, too, with what Hawkstone's first guidebook, published in 1783, described as the 'Adam and Eve of this delightful Eden'. The couple lived in a hovel fitted up with stuffed birds, part of Sir Richard Hill's philanthropic ideal to keep all the poor of the parish gainfully employed at Hawkstone. You can't see it going down so well now at the Job Centre ('Wanted, hovel keeper, experience with stuffed birds an advantage').

The whole circuit is about 10 miles and takes at least three hours to walk, but there are short cuts for the faint-hearted, and an alternative to the Swiss Bridge, if you suffer badly from vertigo. This has been copied from the original, described by Thomas Rodenhurst, who wrote the first guide, as 'made of solid, rude oak'.

The present bridge is also oak, a whole tree, scarcely a foot wide, flung across a very deep gulley. It has handrails, but even so your knees go curiously wobbly in the middle of it, and you are glad to reach the other side. From there you wind round, losing your sense of direction for the umpteenth time, and are brought up to Gingerbread Hall.

Not much was left of this particular folly by the time the restoration began. There was a stone floor, two post holes and various recesses in the back wall of the shelter. A photograph from about 1870 shows it very clearly, though, a thatched structure supported by two upright posts, and the restoration has followed this exactly.

The same picture shows Martha Higginson, in charge of the gingerbread and lemonade, posing on the bridge leading to the hut. By the 19th century, Hawkstone had acquired a more folksy patina than it had in the 18th century, when Gingerbread Hall was called by its original name, the Temple of Patience.

There was a philosophical underpinning to gardens then, which we have lost now, a lot of talk about man's relationship with the landscape, a desire to do in three dimensions what painters were doing in two, and to create monumental scenes that might have come from the canvases of Salvator Rosa, or Claude or Poussin. Now the Temple of Patience is a loo stop.

You had to live in the right place, though, to be able to bring off these effects. You could hardly be sublime in the pancake lands of East Anglia. The Welsh borders, Tintern, Piercefield, Hawkstone, had the right credentials: rock that weathered into sufficiently terrifying formations, and views that made the climbs worthwhile. From the top of the monumental tower, you can see 13 counties. And a lot of golfers.

You also had to have money. How long did it take Sir Rowland's men to chip away the steps that they cut in solid faces of rock? How long to make the grotto, said to be the biggest in Europe? Work at Hawkstone went on so fast that Rodenhust's guide went through nine editions trying to keep up with it.

The restoration is an astonishing achievement. None of the buildings had survived in a complete form, and much of the circuit walk had been obscured by the rampant growth of wild rhododendrons. The only way the surveyors could work out the routes of the original paths was by climbing to the tops of the tallest trees in each area and directing operations from these swaying perches.

Hawkstone's 18th-century visitors used to stay at the hotel at least two or three days, sailing on the artificial Hawk River, marching over to take in the Iron Age fortifications at Bury Walls. You have to substitute golf for sailing now, but you can still catch at Hawkstone the ghosts of Dr Johnson's day.

Hawkstone Park, Weston-under-Redcastle, Shrewsbury, Shropshire SY4 5UY is open daily (9am-5pm) from the beginning of April to the end of October. Admission pounds 4.

(Photograph omitted)