Nobody rambles across Tokyo. It is the ultimate megacity: a vast web of suburbs – of small cities, really – radiating out from a hub of skyscrapers. More than 30 million people live within 30 miles of its centre.
A city this big and complicated can only function because of its extraordinary mass transit system, which shuttles millions of workers to and from its suburbs each day.
But I wanted to experience the city at walking speed. Somewhere under the concrete, the tower blocks, the monorails and the overpasses, lie other versions of Japan: the culmination of thousands of years of island history, presided over by an imperial family that still traces its descent in an unbroken lineage from the sun god, Amaterasu.
This strange combination of modernity and tradition is what's so intriguing about Japan: bullet trains and tatami mats; pachinko parlours and tea ceremony; concrete ugliness and a reverence for natural beauty; the kitsch of Hello Kitty and the simplicity of haiku.
So one bright December morning I started my walk across Tokyo from the summit of Mount Takao. Takao is in a nature reserve on the western edge of Tokyo's municipal boundary. It is roughly 40 miles as the crow flies to the heart of the city. With me that first day was Mr Suzuki, a handsome, 68-year-old former airline steward who had taken up guiding in retirement.
We had reached the summit by cable car, after a 90-minute train ride from downtown Tokyo but from here on, we were travelling by foot.
Looking west from the summit, we could see mile upon mile of velvety green mountains, home to wild boar, monkeys, barn owls and flying squirrels. But east of us lay the urban sprawl of Tokyo: the city fanning out from the bay, its central district a hub of distant grey spikes.
View Walking the world's megacities: TOKYO in a larger map
It would have been serene, except the mountain was heaving with visitors. Tokyo is short of green spaces and Takao is a popular place for day-trippers. Most had come to admire the late autumn colours of the maple leaves. They were snapping pictures on their mobile phones and "oohing". Some were in full alpine kit, with walking poles, tin mugs jiggling on their backpacks, and gas stoves. But no one was going as far as me: I had four days' walking ahead of me before I reached central Tokyo.
At the base of the mountain, Mr Suzuki and I ate a bowl of buckwheat noodles at the Maple Leaf noodle shop. Mr Suzuki spoke English with the careful pronunciation and vast vocabulary of the autodidact. He wanted me to clarify a few points of translation: "Marcel-san. Should I say soba with grated taro, or soba with grated yam?"
And in return, I questioned him about the mysterious Japanese aesthetic principle of wabi-sabi.
"Very difficult to explain in simple words, Marcel-san," said Mr Suzuki. "This is part of the Japanese spirit. Nothing permanent, nothing perfect, nothing finished."
Wabi-sabi is most visibly expressed in the arts that are unique to Japan. There is a hint of it in the apparent artlessness of Japanese flower-arranging; in the wonky teacups that are prized for tea ceremony; and in the sombre colours and weathered old stones of Japanese garden design. Wabi-sabi belongs to premodern Japan: the Japan that predates manga, industrial development and the armies of salarymen riding commuter trains to work. But it retains some significance, particularly to older Japanese people, for whom it also seems like an ethical imperative.
For the next hour or so, we found a few wabi-sabi features in the landscape. Clear mountain streams were running beside the road. There were traditional wooden houses with tiled roofs, citrus trees in their gardens and strings of persimmon drying in the sunshine. In one house, I could see an old woman kneeling on her floor as she worked on a huge piece of embroidery.
We were walking along route 20, which follows the line of the Koshu Kaido, one of the five arterial roads of medieval Tokyo. We passed a marker showing 30 miles to Nihonbashi – the bridge in Tokyo from which all distances were traditionally measured.
The road was lined with two rows of gingko trees, which had shed their leaves in piles on the pavement.
"The gingko leaves, like heaps of gold," announced Mr Suzuki, as though roughing out the draft of a haiku.
Around us, the city was still on a human scale, with small, artisanal shops: a man making tofu late in the evening ("Very difficult work, Marcel-san. Hard to compete with supermarkets"); a woman selling pickled turnips; various wagashi shops, which sell the bean paste sweets with seasonal themes that are served with thick green tea as part of the tea ceremony. But gradually, the city began to grow higher and denser around us.
At Hachioji, an overpass over the road seemed to signal the onset of the city proper. Suddenly, we were surrounded by vending machines covered with pictures of Tommy Lee Jones that dispensed cans of hot and cold instant coffee. "No ordnance preventing this," said Mr Suzuki. "Americans think it's very funny to find Tommy Lee Jones here. But you know he went to Harvard with Al Gore."
Mr Suzuki and I parted at Hachioji. He had set up his mobile phone as a pedometer. "That is the farthest I have ever walked, Marcel-san. Thirteen kilometres!" I was sad to see him go.
I fell asleep at 9pm, exhausted from the walk and jet lag. At some point during the night, my phone rang with vague communications from Britain: a child was a speaking elf in a Christmas play, something about my mother-in-law. My jet lag felt less like Lost in Translation and more like Life on Mars.
The next morning, the weather was raw and grey. I followed the yellow gingko trees along route 20 and over the Asa river. My breath came in smoky puffs.
For the next two days, I walked across grey Tokyo suburbs in light rain, carrying a change of clothes in my backpack and listening to a Japanese tutor tape. I used sign language and half a dozen Japanese words to order lunch and dinner in noodle bars. I relied on Tommy Lee Jones for coffee and tea.
I had the exhilarating feeling of being immersed in a mysterious, distant world. At night, I was reading Richard Lloyd Parry's book People Who Eat Darkness, and I couldn't improve on his description of the excitement of being in Japan: "Every morning it takes her by surprise – the sudden consciousness of profound difference. Is it something unfamiliar about the angle of the light, or the way the sounds register in the summer air? Or is it the demeanour of the people on the street and in the cars and the trains – unobtrusive, but purposeful; neat, courteous, self-contained, but intent, as if following secret orders?"
Even at its most grey and mundane, there was something extraordinary about the city. It manifested itself both in strange absences – litter, overt conflict, graffiti, noise – and in the positively unusual: the huge numbers of people in surgical masks, the baffling signage, the sedate cyclists beside me on the pavement, the schoolboys in their Prussian uniforms.
No one greeted me, no one tried to talk to me, no one ripped me off, and I never ate a bad meal. It seemed perfectly natural for a gaijin (literally, an outside person) with no Japanese and a big backpack to be yomping through the drizzle.
Every now and again, I'd have what I thought of – no doubt, inaccurately – as a moment of wabi-sabi. I'd see a little temple, or a tiled house with an orchard of persimmon trees around it.
I walked past miles of industrial hangars echoing with the sounds of heavy machinery, and through residential areas that had, within living memory, been open fields.
Gradually, I became familiar with the way the city rises and falls. Hotels, skyscrapers and big department stores were clustered around the train stations that link the suburbs to the transport system. Some of them were like miniature Tokyos with high-rises and neon signs – the suburb of Tachikawa had its own red-light district, where hostess bars and karaoke clubs were housed in the upper stories of tall buildings. But half a mile further on, the architecture would shrink again, and the landscape would revert to residential suburbs of two-storey houses.
Modern Tokyo is the product of two cataclysmic 20th-century events: the 1923 earthquake and the second world war. The destruction gave planners a free hand to design a city that was unsentimentally efficient and dynamic. But there is little visible remnant of that older Japan. I looked in vain for the delicate imperfections of wabi-sabi.
At times, the urbanisation seemed relentless. Whenever I saw something that wasn't concrete, I had the urge to snap a picture of it. On my third day, as I raised my camera to take a picture of some aubergines growing on a tiny plot of land, I was struck by a strange realisation: I had become a Japanese tourist.
That lunchtime, I found a tiny restaurant, run by a couple who were at least in their 70s and possibly a decade older, opposite the campus of Tokyo Gakugei University. I banged my head on the low pole by the entrance. There were half a dozen tables inside and one other customer, slurping his noodles companionably. Its authenticity was only enhanced by the fumes from a paraffin stove and a television showing a Japanese quiz show.
I ordered by pointing at a photo in the menu and using a phrase I had learned from my tape: kore okudasai – this, please.
I watched the quiz show while the elderly chef rattled pots in the kitchen. Then his elderly assistant slowly brought me a pretty lacquered tray with tempura, soba noodles, pickles and a satsuma. I took a picture of it.
The number and visibility of very healthy, active older people is another of Japan's minor oddities. Life expectancy in Japan is very high. But while its citizens are living longer lives, fewer and fewer of them are being born. The country has actually been shrinking at the rate of about a million people a year. The government has projected that the population of the country will have shrunk by a third by 2060. The prospect of a collapsing, senescent population struggling to maintain its living standards and its infrastructure seems like a vision from a dystopian novel, but it's something the Japanese are having to take seriously.
Kichijoji, where I spent the third night of my walk, is only 10 miles from Tokyo and considered the city's most hip and desirable suburb. It's Tokyo's Williamsburg, or Notting Hill. It has little bars and vintage clothing shops, and, best of all, beautiful Inokashira Park, from where I set off in the morning and followed the course of the river Kanda all the way into the city.
This was the best walking yet. The sun was bright, the maples and gingko trees red and gold in the light, and the river was full of big, fat carp. There were residential houses on both sides of the river. Just a few hours from my final destination, I felt like I'd found space and tranquillity. From here, I emerged into the city proper, close to the big towers of Shinjuku, Tokyo's administrative centre.
After days of steady walking, I was unprepared for the impact of the big city: its chic, black-suited crowds, its towering neon escarpments. Tokyo has a purposefulness and an energy that resembles Manhattan's, but on an even bigger scale. I gawped at the Blade-Runner world of Akihabara, and went into an eerie maid cafe. Inside, the colours were bright, like the set of a children's television programme, where desexualised waitresses in French maid outfits speak in put-on squeaky voices.
At Tsukiji, Tokyo's awe-inspiring fish market, I ate sushi and marvelled at the produce: tuna fish the size and shape of human torsos, every kind of crustacean, bivalve, mollusc and invertebrate that this seafood-crazy nation eats.
At Nihonbashi, the bridge where the five arterial roads of medieval Japan meet, I officially concluded my walk. The bridge was built in 1911 and seems almost ancient in modern Tokyo. But the city's lack of sentimentality about the past is evident from the way the bridge's clean lines are boxed in by a concrete flyover.
There was something energising and intoxicating about being in the city, but I missed that sense of an older, more timeless Japan. And then, finally, from the 30th floor of my hotel, I rested my weary feet and looked back across the teeming city to the green slope of Mount Takao. Behind it hovered Mount Fuji, as luminous as a painting on a silk scroll.
