Gertrude Jekyll, the late, great British garden designer, once wrote: “Why should a garden not be childish? Perhaps when it truly deserves such a term it is the highest praise it could possibly have.” The highest indeed - in Britain, we relish the eccentric and the dreamlike in our gardens. We have a tradition of building places of fantasy in them: follies, grown-over ruins and grottoes glistening with crystals. And this is the stuff of childhood – it’s all about imagination.

Our greatest fantasy gardens remind us of our favourite books: the Wonderland into which Alice fell; the silvery tree city of the elves in The Lord of the Rings, with its sacred glade and water in which the future is told; and the fairy forest of A Midsummer Night’s Dream, “quite overcanopied with luscious woodbine, with sweet musk-roses, and with eglantine”.

The grotto (a cave-like structure that may have several chambers and usually contains water) is perhaps the most intriguing part of the fantastical garden tradition. They can be frightening (many have dark corners and passageways), but can be comforting, too; almost womb-like. Leonardo da Vinci wrote of one he visited: “Two contrary emotions arose in me: fear and desire, fear of the threatening dark grotto, desire to see whether there were any marvellous things within it.”

The British seem to have a particular obsession with them – at one time, the country had hundreds. During the Renaissance, Italians erected copies of Roman grottoes to give their gardens atmosphere. In the 18th century, the grand tourists saw them – and fell in love. Soon, everyone was building one.

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One of the best remaining today is at Hawkstone Park, in Shropshire – built in 1790, it’s a series of dark tunnels and chambers carved into the hills. The beautiful grotto at Stourhead, in Wiltshire, was built in 1748. The main chamber contains a pool fed by springs and a reclining statue of a water nymph. An inscription reads: “Nymph of the grot, these sacred springs I keep, and to the murmur of these waters sleep. Ah! Spare my slumbers, gently tread the cave, and drink in silence or in silence lave.” An opening in the grotto provides a view towards a lake.

Fantasy elements are not, however, confined to historical gardens. Ivan Hicks, one of Britain’s most celebrated creators of contemporary gardens, has been coming up with them for years. “The key ingredients for a garden of imagination are atmosphere, seclusion and beauty,” he says. As a child, he spent time playing in overgrown gardens and woods; when he grew up, he travelled around the world with Edward James, the eccentric millionaire poet and sponsor of Salvador Dali and other surrealist artists. James was responsible for the world’s greatest fantasy garden, Los Pozas, set more than 2,000 ft above sea level in the tropical rainforest of Mexico.

Hicks is fascinated by trees and the myths that surround them. “My work is about going back to the woods,” he explains. “I try to design places that put you in touch with nature and other worlds. It’s about escapism, dreaming.” In the Enchanted Forest, designed by Hicks at Groombridge Place, in Kent, is the Mystic Pool, a pond overhung with mirror pieces. “Water hassacred symbolism in many spiritual traditions,” he says. “We all appreciate this intuitively. Beneath the pool is another world, and it’s reflective.” Groombridge includes the Dark Walk, a raised walkway that runs through the treetops for a quarter of a mile. “I want people to be in touch with the trees and perhaps to see them as sacred beings,” Hicks says, reminding us of Tolkien’s talking trees.

Other features of the Enchanted Forest include the Serpent’s Lair, the Standing Stone and the Village of the Groms. “The Groms are woodfolk,” Hicks says. “It’s a story line for kids. I like them to imagine that the Groms are out at work during the day and, while they’re out, you can see where they live.”

The latest addition to the fantastical tradition is the new Collector Earl’s Garden, created in what used to be a car park at Arundel Castle, in West Sussex. Open since May, it was conceived by Isabel and Julian Bannerman, a husband-and-wife design team who have been working together since 1983, and is intended as a tribute to Thomas Howard, the 14th Earl of Arundel (1585-1646), an eccentric who travelled extensively. Reminiscent of a far-off land, it is filled with dreamy features, among them Oberon’s Palace, a grotto-like building with a fountain.

“My initial idea for a new garden was to create somewhere spiritual,” says the Duchess of Norfolk, whose family lives in the castle. “I wanted a place that touched the soul – somewhere mystical.”

Oberon’s Palace is a copy of the design for a stage set at a party thrown in 1611 for Prince Henry, the son of James I. The brilliant structure, which has Arundel Cathedral as a backdrop, is domed and has grotto-like walls stuck with shells. The garden also contains two temples and a long, domed pergola, in and among which are exotic plants such as date palms, tree ferns, bananas, bamboo, agaves and cannas, intended to seem foreign. There is a lot of water, too, continuously spouting from the fountain in the palace and flowing from a temple into a pond. “The water in the garden is crucial,” the Duchess says. “Water can make or break a design, and it is a spiritual element – vital in a garden like this.”

As well as a fascination with magical beings, such as gnomes, it seems we also have a fondness for the dwellings of our ancestors – specifically those that have been ruined or lost. There is something fascinating about a building or garden that has been left to its own devices. At the Lost Gardens of Heligan, near St Austell, Cornwall, visitors can walk around an entire garden and valley that were once overgrown and forgotten. They may even wish things had been left a little ramshackle.

And at Dewstow, in Caerwent, South Wales, you can explore an underground Grade I-listed grotto garden buried for 50 years under a farmyard until its recent rediscovery. The seven-acre site, some of which is still to be resurrected, is made up of ferneries, a warren of tunnels and ponds designed by the Victorian/Edwardian landscapers James Pulham and Son, who specialised in “naturalistic” landscapes of rocky outcrops and ravines. John Harris, the present owner, has filled the underground caves with ferns and exotic flowers, an attempt to recreate the feel of the original garden.

A ruin also holds a certain charm. At Nymans, near Crawley, West Sussex, the quarters of a large house that burnt down in 1947 are now roofless and romantically ruined. Great arms of wis-teria and roses climb through the ruins, claiming them.

As well as containing lost worlds and buildings, the fantasy garden seems to insist that we get a little lost ourselves. Mazes and labyrinths traditionally perform this role. At Longleat, in Wiltshire, there are five, including a Mirror Maze and a Love Labyrinth made of 853 roses. As the law of the maze says, we all have to get a little lost to find what’s real. The fantasy garden, with its overgrown passageways, pools, grottoes and groves, might just be the place to do so.

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