Britain has some remarkable places. If we discovered them on the other side of the world, we'd soon be writing home. Film-maker and novelist Tom Connolly explores parts of Kent that have fuelled his creativity

There is a particular adventure in feeling that we have reached the edge of land, in the illusion that we have discovered uncharted territory, even when we do so close to home.

In north Kent, where the Thames transforms from river into estuary, the Cliffe Marshes on the Isle of Grain offer an alternative face to the Garden of England, equally as memorable as the oasthouses and orchards, and arguably more fascinating. It is a prairie-sky landscape that is beautiful and desolate, an otherworldly place within an hour of London.

I first went there 20 years ago, roaming without purpose across my home county with my friend Dave Turnbull, then a fellow cameraman, now a Dorset blacksmith. Driving towards the setting sun, we had been drawn into a flat unpopulated landscape and were oblivious to the fact that the Thames was nearby, snaking its way through the marshes we now crossed.

We drove to the end of an unmade road flanked by bullrushes, then continued on foot, tightrope walking across a pipe that bridged a drainage ditch and landed us in a maze of weather-ravaged corrugated-iron huts, animal pens and bird traps. On a fence were nailed a line of rabbit pelts and a dead jackdaw. Painted haphazardly on to a railway sleeper were the words "JACK RIPON LAND. STAY OUT". We looked back. The car was already a speck on the horizon.

We had strayed into trespass that evening, but if you keep to the footpaths on Cliffe Marshes you will feel welcome to enjoy this place of unlikely and peculiar beauty. Back on that first, enchanted evening, as we debated whether or not to hang around and find out who Jack Ripon might be, we heard a sound, a soft sound so low and directionless that it seemed the sky had begun to breathe. It came from nowhere but was everywhere. It had no discernable beginning or end, instead it inserted itself seamlessly into the air. "God blowing through a bottle," Dave murmured.

We found ourselves staring open-mouthed across the flatlands at the mirage of a pearl-white cruise ship gliding above the fields. The deep sound came again, from the ship's funnels, and this time the ground vibrated. We ran towards the ship and a low sea wall came into sight, a pencil-thin detail that had been hidden in the dusky contours of the landscape. We clambered up the wall and the Thames revealed itself, wide and calm, saturated by the colours of sunset and reflecting with mirror sharpness the gas burners of the refinery on the opposite bank.

Breathless from running and exuberant at stumbling upon the transformation point of river into sea, this place filled me with the same thrill that first setting foot on Manhattan had done. The comparison may seem strange but travel is, for me, about the renewal of wonder, the possibility of discovery. Whether exploring my home county of Kent or the other side of the world, a geographical landscape replenishes the landscape of one's own imagination. Many of the places that do this are close to home, tucked away off the beaten track, places that, should we encounter them on the other side of the planet, we would remember and tell everyone about them.

I return to the Cliffe Marshes in all seasons, most recently in June, starting at the RSPB reserve at Cliffe Pools – a mixture of brackish lagoons, freshwater pools, and salt marsh offering protected habitat to wading birds and wildfowl, and rarities such as water voles, emerald damselfly and green hairstreak butterfly. It is also the gateway to a wide vista of blemished beauty, where the changing light repaints the mood, hour by hour.

In cinematic terms, this is the terrain and light of Terrence Malick's Badlands, the big skies of Days of Heaven. Those two films shaped my love of cinema and it is no coincidence that I return to this challenging, painterly landscape, which casts a similar spell as the widescreen poetry of those stunning cinematic depictions of rural America.

From the Pools, the Saxon Shore Way leads out into this beguiling landscape, most of it grazing land farmed by tenant farmers and owned by the the Port of London Authority. I walk parallel to the skeletal structures of a cement works conveyor belt and towards the distant twin chimneys of Tilbury power station. The birdsong is loud, musical and constant across acres of buttercups spread out in thick swathes. Butterflies flash white then disappear into thin air. A beef herd grazes in the long meadow grass and above them vast container ships glide soundlessly through the landscape on the hidden river.

Cliffe Fort and Cliffe Creek, ruined and deserted, hint at the marsh's historical role in defending the river from invasion and at the Victorian prosperity which the cement industry brought to the peninsula. (Portland, Roman and Medina cement, Portland stucco and plaster of Paris were shipped from the creek). At the creek, I leave the Saxon Shore Way and follow a footpath that hugs the river bank and pass a rusty abandoned pier hovering above the pale-green water. Here, at the north-west tip of the peninsula, the expanse of marsh is stunning to behold.

Wild grasses – sea barley and annual beard grass – sway to the hum of river traffic beneath an arching, fathomless blue sky. A dozen white horses run in circles among earth mounds that betray the position of an old munitions site. From one of the flooded explosion pools, an egret takes flight. Cliffe church sticks its head out above the trees, a reminder that though at the edge of the world, you remain part of it.

The Thames curves eastwards and widens as it readies itself to become open sea. The lush, green marshes and majestic river form an increasingly dramatic canvas with the graphic industrial lines of the Coryton refinery on the other side of the water. Arrive here, at Egypt Bay, at dusk, as I did by accident 20 years ago, and the view transforms before you, the sparkling lights and fluttering flames of Coryton assuming dominance in the darkening sky and the Thames turning inky black as if to oblige in reflecting the light show.

Charles Dickens described the north Kent marshes as "wilderness", and even at its most serenely beautiful there is a wildness to the clefts in the landscape that offers inspiration to the visitor. Head east from Grain towards the neighbouring Isle of Sheppey and, at the last point on the mainland, you will find Bedlam's Bottom, a creek on the Chetney marshes. Any place on the map with a name like that demands a visit and this inlet is a wonderful walking (and thinking) spot. It combines the prettiness of north Norfolk with the moodiness of a distant horizon incited to drama by Kingsnorth power station and the jetty cranes at Grain.

Muted olive-green farmland sits against unquenchably black mudflats. A decayed tanker lies on the low tide, draped in treacle-thick mud, among fissure-like inlets and saltings which have carved themselves graphically into the mud and fields. Ancient, gnarled hawthorn bushes lean steeply with the prevailing winds. (There's a reason they call it "windthorn" here.) The public footpath on Raspberry Hill Lane is your gateway to this deeply atmospheric place.

Even easier to find than Cliffe and Chetney are Nagden Marshes, between Faversham and Whitstable. A good way to access them is to park up at the renowned Sportsman pub and head west, parallel to the marching pylons, into a summer scene of viper's bugloss, black-headed gulls and bait diggers on a low tide. A cool, soft, salty breeze straddles these and the green fields and cherry orchards are fallow fields of orange, brown and rusty hues.

A gang of cherry pickers sit in the shade of a fierce sun, yet the inland sky behind them is a canvas of storm clouds, the gaps in which, look like petrified lightning. Cleve Marshes become Graveney Marshes and they, in turn, give way to Nagden Marshes as you approach Faversham Creek. Here, the sea defences have been let go and create graphic shapes on the beach. A lichen-covered sea wall teems with red ants and there is colour laced into every detail of the landscape.

In the mid-1980s, when I lived at Seasalter, this exposed marshland was the perfect cure for a student hangover in winter, such was the clean, icy quality of the winds. The pools, left by the receding tide reflected a silvery sky both painterly and bleak. It is timeless, an exposed place defined by the elements, by seasons, tides and moods, sometimes hostile, other times meditative, always fortifying.

This is a Wyeth landscape, redolent of the tones and themes and interplay with landscape that the great American painter, Andrew Wyeth, devoted his life's work to. Wyeth himself wrote: "I prefer winter and fall, when you feel the bone structure of the landscape. Something waits beneath it, the whole story doesn't show."

And this is the point of these Kentish nooks that lay a little off the beaten path. They are untamed, visceral and exposed, sometimes sharing their space with industrial sprawl. But the undeniable rawness of these places is part of the story. They are also astonishingly exquisite guardians of the most magical light, teeming with life and fertility and beauty, reflective and inspirational landscapes with an extraordinary sense of the huge sky above us and the vast space within.

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