Gardening: A garden of pure follies

Studded with a series of follies and temples, Painshill Park beckons you ever onwards. It is a magical place at any time of year, but in winter the superb quality of the design is revealed and this year there is something very special happening in the grotto.

Painshill was created by Charles Hamilton in 1738, and soon became one of the most visited landscape gardens in the country. Hamilton was not a particularly wealthy man, nor was the site particularly prepossessing; by 18th-century standards it was not even large. Nevertheless, by improvement of the sandy soil and by his clever design, Hamilton managed to create a magnificent garden.

The visitor, then as now, embarked on a walking circuit that took a couple of hours, almost as though attending a theatrical performance - the follies and temples, woods, hills and water would appear and disappear on the journey like characters in a play, always with that tantalising element of surprise. "Pray follow me to Mr Hamilton's," wrote Elizabeth Montagu in 1755. "I must tell you it beggars all description, the art of hiding art is here in such sweet perfection that Mr Hamilton cheats himself of praise."

Hamilton was, first and foremost, a plantsman, and the ground was "dressed and clumped with flowering shrubs, sweet trees and flowers". Among the trees, Hamilton's pines were admired by his friend Walpole and his firs by Carl von Linne. In fact, more than a hundred of his original specimens still remain, including the largest cedar of Lebanon in the country, now some 32ft in girth.

The miracle is that, more than a quarter of a century later, we can experience Painshill almost as Hamilton intended, for the garden restoration - started in 1987 by the admirable Painshill Park Trust - must be one of the most authentic ever undertaken.

The amphitheatre, for example, a grassy oval at the start of the circuit, has been surrounded by tiered ranks of evergreens that would have been available in Hamilton's day. Beyond, past an avenue of dark trees, is the little Gothic temple from which there is a totally unexpected view of the lake, with the Chinese bridge crossing on to Grotto Island. In keeping with the 18th-century precept, "lose the object and draw nigh obliquely", the route there is indirect, taking you down the side of the hill and across a grassy peninsula. This area is planted with exotic shrubs, many of which were early introductions from America.

Having reached the grotto, a spacious, limestone-clad cavern approached by a narrow tunnel, the visitor cannot fail to be amazed. By 1948 the original roof had fallen in but, although the restoration is still incomplete, the roof has now been made safe and part of the interior is once again hung with the crystalline stalactites that, it was claimed in 1791, "rendered it so brilliant that it seems a true Fairy Grotto". The cavern opens directly on to the lake, allowing the light to filter in, and, appropriately, it is here, for a few days during the Christmas holidays, that children will find Santa Claus and his well-filled sack of toys.

Adults will probably be more intrigued by the restoration technique: a wooden cone forms the base for each stalactite, to which individual crystals of gypsum, calcite, quartz and fluorite have been glued by hand. It is tedious and expensive work, which has temporarily ground to a halt because of lack of funds. But eventually the grotto's floor will be covered with sand and cockleshells and the extensive water features will be restored.

The atmosphere changes from grotesque to melancholy as you approach the next folly on the circuit, a ruined Roman mausoleum - planted round with yews to evoke a mood of gloom and remind us that earthly pleasures fade. Not so the next structure, the recently restored Turkish tent, which commands a panoramic view (said to have been Hamilton's favourite) over the lake. It would be the perfect place - and can be hired out - for a champagne picnic, with its brick structure draped with heavy-duty blue-and-white canvas and finished with a dashing metal topknot.

Much is still to do. There are plans to replace the five-arch bridge; the now vanished temple of Bacchus will one day reappear, as will the boat house, the bath house and the hermitage (Hamilton's hermit was promised the then enormous sum of 700 guineas if he succeeded in remaining for seven years in silence, but within three weeks he was found drunk in the local inn). But even without these attractions, there is still plenty more to see.

The Gothic tower beyond the Elysian plain and alpine meadows was the first folly to be restored; Hamilton's vineyard, from which he produced sparkling wine said to equal champagne, has been replanted and the ruined abbey, an eye-catcher originally built to disguise the site of Hamilton's commercially disastrous venture into brick-making, has been reinstated.

It was a sad fact that Hamilton was a poor businessman. In order to "make a pretty Landskip of his possession" he was forever begging and borrowing money from his friends. Eventually enormous debts forced him to sell up and he moved to Bath where, as a poor but jaunty old man, he could be found working on other people's gardens. His spirit, however, resides at Painshill, at peace in the knowledge that his beloved place is in safe hands.

Painshill Park is at Portsmouth Road, Cobham, Surrey, KT11 1JE (01932 868113). Santa Claus will be in the grotto this weekend and next, from 11am to 3pm. Book places as space is limited