When Anna Pavord wants the world to stop, she heads to the unshowy, serene tranquillity of Mapperton in Dorset
The first purpose of a garden is to be a place of quiet beauty such as will give delight to the eye and repose and refreshment to the mind," said the plantswoman Gertrude Jekyll in A Gardener's Testament, written towards the end of her life. She was thinking of the subject from an owner's point of view, but her definition fits what some garden visitors look for, too.

The gardens I most value are those where you feel, quite palpably, that by passing through the garden gate, you step into a different world, one that has nothing to do with anger, frustration or sorrow. As a Hindu leaves his shoes at the entrance to the temple, you temporarily cast off life's grubbier aspects and float. Tranquillity.

In May, the place I go to find that is Mapperton, near Beaminster in Dorset. It starred recently as the setting for the BBC's remake of Tom Jones, but, at heart, it's a quiet garden, with none of the great set- pieces that star gardens usually have. You won't find here the blazing herbaceous borders considered de rigueur in old country houses. Mapperton doesn't try to show off with collections of rare or stylish plants. But sitting on the edge of the great lawn to the north of the house, gazing over the garden hidden in the valley below, you want the world to stop, there and then.

It reveals its delights slowly and elegantly. The drive leads you down past a handsome stable range of the mid-17th century, set at right-angles to the house. Opposite this is the entrance to the garden, dominated by lead eagles perched on top of the gate piers. Six drums of clipped bay lead through the entrance court to the front door of the house. To the right, a medieval church, All Saints, shuts off the courtyard to the south. Sometimes, the whole enclosed square swims with the smell of tobacco flowers thickly planted in the beds.

A path leads off to the left to bring you round the house and out on to a massive lawn, surrounded by tall walls. Wisteria, magnolia, garrya and ceanothus all benefit from their shelter, but the thing you most notice here is the magnificent multi- stemmed Acer griseum, planted in the corner made by a projecting wing of the house. Restraint is one of the most difficult skills to acquire as a gardener and every time I see this tree, I mutter the mantra, "Less is more. Less is more..." It hasn't worked yet, but I'm still hoping.

On the lawn, you are at the same level as the cattle and the sheep grazing in the rough pasture that rises steeply on the other side of the valley. Down below, is Mapperton's great surprise: a superb formal garden with terraces, pool, pergola and yew topiary.

It's completely hidden until you get to the lip of the lawn and must once have been part of the original 17th-century garden. What you see now is c1919, part of the remodelling of Mapperton carried out by the Laboucheres, who bought the estate from the family that had owned it for aeons before that.

You can get down into it by several ways. One narrow set of steps drops down close to the boundary wall and delivers you at the doors of an orangery, set with its back against the wall and a view down the whole of the narrow valley garden. Wider, but equally steep steps lead between drunken mounds of lavender and arrive close to the thickly clothed pillars and roofbeams of the Peto-esque pergola. Wisteria, vines and clematis fill the air with mad curls.

Either route will eventually lead you to the centrepiece of this part of the garden. This is the raised octagonal pool, supported by scrolls of stone and surrounded by random paving. Little herds of yellow daisy- flowered bidens have seeded into the cracks. Steps rise up either side of the pool between important balustrades of yew to small summerhouses, thoughtfully provided with fireplaces. From these dark little caverns, you peer back down between the flanking yews to the pool, plain and dignified.

The land falls steeply away from this part of the garden to make another terrace in the valley below. A Rapunzelesque tower with a pointed roof marks the boundary between the two sections. Below the tower is a long 17th-century canal, with clipped yews along the sides, curved sofas of yew in the middle and spiky yuccas marking the end of the formal layout.

But the garden, now in a totally different mood, continues on down the valley. The grass gets longer, reaching out in spirit to the surrounding farmland. This what I think of as the Hillier's Manual garden, a collection of rare shrubs and trees made in the 1960s by Victor Montagu, father of the present owner, the Earl of Sandwich.

The point of Mapperton, though, is not its parts but its whole. Your eye absorbs the gentle colour of the brick wall that holds in the formal garden on the far side of the valley. It notes the supremely graceful stand of Scotch pine (Pinus sylvestris) that lean out on a promontory the far side of the canal garden. This is not a garden where you take busy notes of plant associations, though it is a model of how much can be achieved with relatively little planting.

Anger, frustration and sorrow may be the lot of the garden's owner, with few grants available for garden repairs and costs spiralling way off the balance sheet, but hell for him equals heaven for visitors.

The garden at Mapperton, two miles south-east of Beaminster in Dorset is open daily until October (2pm- 6pm). Admission pounds 3. There is a tea room, but the house is open only to parties of 15 or more who book in advance. Telephone 01308 862645 for details.

Other gardens to visit

The garden at Villa Lante, which crowns the small hill town of Bagnaia, near Lazio in Italy, marks the beginning (almost) of the story of the pleasure garden in Europe. Though a shadow of what it was when Cardinal Gambara made it in 1568, it is still the least changed and best preserved of any of the great gardens of the Italian Renaissance. Lazio is open daily from 9am to 5.30pm. Admission, 5,000 lira.

Kasteel Hex at Heers in the Limbourg region of Belgium was built in the middle of the 18th century by Count Charles-Francois de Velbruck, Prince- Bishop of Liege. He made the most of a slight natural rise (rare in Belgium) to lay out rather grand formal gardens to the south and west of his house. Visits by appointment (telephone 0032 12 74 73 41). Admission, 300BF.

"My garden is my most beautiful masterpiece," said Monet about Giverny, his Normandy home. Go there for inspirational use of colour, not for ideas on garden layout. Open Tues-Sun from April to the end of October (10am- 6pm). Telephone 0033 32 51 28 21 for admission.

Sir George Sitwell, like Harold Peto and other architect gardeners, was heavily influenced by Italy and in his garden at Renishaw in Derbyshire, he worked with water, statues, vistas, hedges and evergreens. Open from May to 13 September, Friday-Sunday and Bank Holiday Mondays (10.30am-4.30pm). Admission, pounds 3.

The thought of actually eating any of the vegetables in the vast potager at Villandry is quite shocking. Rich ruby chard, metallic blue leeks and frilly lettuce in bronze and green are used as richly textured paint might be to make geometric patterns in the nine square beds of the main garden. Villandry, 18km west of Tours is open daily (9am-5pm). For information on admission prices, telephone 0033 47 50 02 09.

Overbecks is a National Trust garden wonderfully situated high above the Salcombe estuary in Devon. Hot colour combinations are a speciality. Overbecks at Sharpitor, Devon is open daily all year (10am-8pm or sunset). Admission pounds 2.40.