Japan is renowned for its bullet trains, but there's no need to rush on the luxurious Cassiopeia, which runs from Tokyo to Sapporo. Danielle Demetriou settles in

It is 4pm at Ueno station, Tokyo. The slow-building daily crescendo towards rush hour is gathering pace, as a grey-hued tsunami of salarymen and office ladies sweeps across the concourse.

But beyond the bento box stands of fresh sushi, the steaming noodle counters, the neon lights of the convenience stores and the surging crowds of tired office workers, there's a less predictable sight.

Sitting at platform 13 is a sleek, metal-grey train with a rainbow-striped logo and a double-decker structure. There is a crowd gathered here too, but they are different from the ones in the station: these are reverential, wide-eyed, digital camera-snapping, 21st-century trainspotters.

Japan has long been synonymous with cutting-edge rail travel. Jostling alongside sushi and sumo, cherry blossoms and misty mountains, neon skyscrapers and robots, its trains take pride of place among the nation's icons. Ever since Japan unveiled to the world its maiden fleet of shinkansen bullet trains during the 1964 Tokyo Olympic Games, the country has revelled in its position at the vanguard of a hi-tech travel revolution.

More than four decades on, the gleaming cavalcade of sleek, safe and blink-and-you-miss-them trains remains one of the most powerful symbols of the nation's economic post-war recovery. But speed is not the only attraction, for in this fast-paced modern age, there is one Japanese train that remains something of an anomaly: the Cassiopeia.

A luxury night train that prides itself on comfort over speed, the Cassiopeia is a sleek beast that transports passengers from the skyscrapers of Tokyo through mountains, rice fields and fishing villages to Sapporo, a city on the northernmost island of Hokkaido.

The Cassiopeia takes a leisurely 17 hours and 12 minutes, travelling at a top speed of 68mph compared with the 186mph of the bullet train so its appeal is clearly not speed. Its charm lies in its luxury, design and comfort, which combine to create a modern appreciation of passing landscapes, but all in traditional rail-travel style.

And so there are plush, rainbow-hued carpets, immaculate stewards, cotton yukatas (casual kimonos) and slippers, newspapers delivered to the door, and an on-board boutique, as well as a dining car serving high-end French and Japanese cuisine.

The icing on the cake is the overnight accommodation: it is the first Japanese train where every traveller on board is allocated one of 83 private en-suite berths of escalating degrees of luxury.

It is little surprise, therefore, that the usual prelude to the three-times-weekly departure is a cluster of trainspotters staging an impromptu photoshoot in front of the train which gleams as good as new, despite running since 1999.

In a country where watches can be set by the trains, the Cassiopeia discreetly slides out of the rush-hour chaos at precisely 4.20pm, as scheduled. On board, the atmosphere is one of subdued excitement. Swaying along the cinnamon-carpeted corridors that run along two floors, I make my way to Room 21 and find the small flight of stairs that takes me to my home for the next 17 hours.

The room is an exercise in compact design. There is a small living-space surrounded by two plush seats that can be rearranged, Rubik's cube-style, into two perpendicular beds. The carpets are deep green and the seating an abstract purple pattern (which, according to an unwritten design rule, seems always to be used on public transport).

In my en-suite bathroom, a small plastic unit contains a toilet, and a complicated contraption pulls down from the wall and doubles as a sink with a constant supply of hot water.

A techno-unit to satisfy the most demanding of gadget-lovers sits on one wall, complete with a small, multi-channel television, heaters, coolers, lighting and an alarm clock.

But the focal point of the spotless room lies elsewhere: a vast, gently curving window frames a technicolor Tokyo landscape of skyscrapers and neon lights. My eyes drink in the passing cityscape until my reverie is interrupted minutes later by a high-pitched cry of "Irashaimasseeeeeee!" ("Welcome!").

I open the door to find a train stewardess with perfectly coiffed hair, a brilliant smile and turquoise silk neckscarf, bearing a cup of green tea. Tea ceremony over, I wander along the spotless corridors with their neat glowing vending machines towards the Lounge Car at the front of the train.

Here, the focus is once more on the view: a long, emerald-green sofa faces one wall of windows and violet swivel chairs are lined up on the other, while the engine carriage can be seen through the front.

Guests gathered here form a motley crew: wide-eyed honeymooning couples, father-son trainspotting teams, and neatly hatted pensioners enjoying the good life, after years of toiling as salarymen. "I've wanted to come on this train for years," says one elderly gentleman with a grey hat. "I'm here with my son now and it's been worth the wait."

By now, the setting sun is illuminating shafts of light through cotton-wool clouds, adding beauty to a drab scene: a seemingly endless sprawl of concrete apartment blocks, grey office towers and flashing shopping centres. As the train nudges itself northwards without any sense of haste, the sun eventually sinks behind the buildings, heralding the arrival of another highlight on board the Cassiopeia: dinner time.

By 8pm, the dining car is almost entirely filled with smiling couples. Although it may not be in quite the same class as the Venice Simplon Orient Express, there is a distinctive and elegant ambience: it is decorated with library-style table lamps, white linen tablecloths and lavish table settings, and the gentle clank of creaking wheels adds to the atmosphere.

There is pink champagne for the coupled-up diners, and Cassiopeia's culinary offerings surpass expectations: from the four-course French menu, including beef fillet and asparagus and crab salad in balsamic vinegar, to the traditional Japanese feast of rice, seafood, tofu and soups in an array of beautiful lacquerware containers.

People-watching aside, the best mealtime entertainment is window-gazing: outside, piles of snow line the tracks as the train stops briefly in the bustling neon station of Fukushima, known for its spring blossoms, before continuing its northerly pilgrimage.

Then, as I tuck into my sweet mochi rice pudding, a smiling steward taps me on the shoulder and pours a glass of pink champagne. He gestures towards an elegant elderly Japanese couple at the other side of the restaurant. I lift my glass in thanks; it seems that even a single female dining alone on the Cassiopeia is entitled to a touch of romance.

Back in my berth, I wrestle with the purple seating and piles of clean white bedding until a window-side bed magically manifests itself before me.

Slipping into a purple cotton yukata, I slide into bed, resist the temptation to watch bad Japanese TV, flick off the lights and am instantly enchanted by the view of the passing night sky through the curving window. A giant butter-yellow moon has appeared in the chill night air, illuminating a nocturnal landscape of small towns, rice fields, empty streets and lone cyclists. All slowly blur into one as I am rocked into sleep and towards a world of train-themed dreams.

At sunrise, a silvery light infuses my berth. The sight that greets me through the window is breathtaking: streaks of white clouds fractured with shafts of light hang above a still expanse of sea, itself lined with snow along the shore.

An island of snowy peaks, dairy farms and mouth-watering seafood delicacies, the northernmost Japanese island, Hokkaido, is a million miles from the fast-paced Blade Runner-style world of the capital. It is hard to believe that the still, white vista before me is part of the same universe as the frenetic Tokyo I left behind.

The in-room intercom system crackles to life at around sunrise, with a xylophone jingle, and a breakfast consisting of a bento box of rice and vegetables bought from a smiling trolley lady, washed down with complimentary green tea.

With only a few hours left until our destination, I make my way down to the lounge as a perfect snowstorm gathers pace: heavy flurries of snow bluster across small fishing towns, coastal beaches and forests. The sense of slowly travelling back in time is compounded by the realisation that the train is now powered by a blue, Thomas the Tank Engine-style engine puffing plumes of black smoke.

Eventually and still at its own leisurely pace, the Cassiopeia pulls into the bustle of Sapporo Station, and back to reality: morning commuter crowds, food halls and convenience stores.

Stepping off the train and swaying slightly as my legs adjust to terra firma, I feel fully relaxed in the knowledge that there is no need to for me to look at my watch: it is precisely 17 hours and 12 minutes since we set off from Tokyo.

Extracted from 'Great Train Journeys of the World', published by Time Out Guides, 16.99

Travel essentials Japan

Getting there

*Direct flights are offered between Heathrow and Tokyo Narita by BA (0844 493 0787; ba.com ), Virgin (0844 874 7747; virgin-atlantic.com), ANA (0870 837 8811; ana.co.jp ) and Japan Airlines (020-7618 3224; uk.jal.com/en ).

Getting around

*There are three train departures a week. The train usually departs Tokyo's Ueno station at 4pm and arrives in Sapporo at 9am the next day, but schedules are subject to change. The official Cassiopeia website ( jreast.co.jp/cassiopeia ) is in Japanese; you can also contact Japan Rail ( japanrail.com ) or book tickets on accessjapan.co.uk , jtbusa.com and japantravel.com .

More information

*Japan National Tourism Organisation: 020-7398 5678; seejapan.co.uk