I had been marching for four hours in 30C heat along the hard shoulder of a busy dual carriageway. With me was a young woman, barely four feet tall. Think Alan Partridge meets Of Mice and Men and you'd be close. The woman was wearing dazzling white pumps and a smile whose dazzle had once matched her footwear but was fading by the minute. She was fresh out of tour-guiding school, and somehow I didn't think this had been on the curriculum.
The day before, I had arrived in Shanghai. With over 25 million inhabitants and growing fast, it's China's economic powerhouse, and currently at number five in the world megacity charts. I had been offered the services of a guide.
"Pah!" I'd said. "I'm an experienced traveller. All I have to do is catch a bus to the edge of the city and walk the 30-odd miles back into the centre. What could be easier?"
At Shanghai South bus station, I spent three hours watching hundreds of buses go by, their destinations advertised only in Chinese characters. I couldn't find anyone who spoke English. In desperation, I jumped on a bus and 20 minutes later was back at Shanghai South. I was as helpless as a newborn. I took my phone out and dialled. An hour later, the woman in dazzling pumps stood before me.
"I'm Miss Fang," she said. "What do you want to do?"
"Go to the edge of the city and walk back to the centre," I said.
"Why?" asked Miss Fang.
It was a reasonable question.
"It is a great way to approach a city," I said, "as it slowly reveals itself, like an image gradually coming into focus."
To me, this sounded suitably Confucian.
"Oh," said Miss Fang, to whom it obviously didn't.
View Walking the world's megacities: Mike Carter in SHANGHAI in a larger map
We sat on a bus for two hours as city's suburbs rolled past the window. We got off at Zhujiajiao, on the edge of Shanghai municipality. Zhujiajiao is a canal town, one of many that sprang up under the Ming dynasty of the 14th century as a commercial centre, built on the network of waterways – man-made and natural – formed by the inundated Yangtze delta.
We crossed the graceful five-arched Fangsheng Bridge, and then wandered the canals, lined with stone Ming- and Qing-era houses, and cedar and peach trees, from whose branches vermillion lanterns hung like pendulous fruit. From many of the trees there hung a songbird in a cage, like a loudspeaker.
Miss Fang bought us food for the walk: qingtuan, rice balls stuffed with red beans and wrapped in wormwood leaves, which the vendor tied up in straw with her teeth; some crunchy dried fish, which got stuck in my throat, amusing Miss Fang no end; and a couple of bags of spicy chicken feet.
"My favourite thing," said Miss Fang.
We hit the road. There was no pavement, so as the traffic thundered past, we walked in the lane with the motorbikes and bicycles, many carrying steel girders that threatened to scythe us in two. The riders wore white gloves and incredulous expressions at the odd couple walking in the middle of nowhere in the afternoon heat. We walked past field after field of strawberries, and clusters of wooden shacks. In the far distance, towards the city, tower cranes filled the horizon, like some Martian army on the move.
As we walked, I asked Miss Fang about her life. She was 23, and had moved from the countryside to the city, part of the greatest demographic shift in modern history as the world's villages empty into its cities. According to US futurist and writer Stewart Brand, by 2050, the world will be 80% urbanised. If China's cities carry on growing at the current rate, Shanghai, whose population has doubled in 20 years, will at some stage merge with Nanjing, Ningbo, Hangzhou and others to form a megalopolis of 88 million people.
Miss Fang told me how she lives in a two-bedroom apartment with five others, how curtains divide the bedrooms. "My boyfriend must have an apartment before I agree to marry him," she said.
It was getting dark as we arrived, some nine miles later, in Sheshan, once a town in the middle of the countryside, but now a suburb of the city's inexorable westward expansion.
I left Miss Fang at a bus stop and walked into an adjacent guesthouse. An ancient woman with leathery skin sat behind the desk. I pulled out my passport. The woman stared at it in horror, then got up and, with great ceremony, shooed me out of the building.
Thankfully, Miss Fang was still outside. She spoke to the woman. "Foreigners must get police permission to stay at guesthouses below three stars," Miss Fang said. She didn't know why. The police wouldn't give permission, and didn't know why either, but did suggest a hotel that would have me.
Miss Fang got her bus. Truly alone now and ravenous from walking, I went into a restaurant. A waitress pointed to a wall of Chinese characters and tapped a pen impatiently on her pad. I wanted to cry. On a side-table were two silver lids. The waitress lifted up the first. A pig had exploded, all ears and tongues and snouts. In the second, the same, only duck, with heads and beaks and webbed feet. I'm sure it was all delicious, but I'll never know. In another blow to my intrepid-traveller ego, I retreated and spent the evening in my room eating the leftover crunchy fish, and crisps from the minibar that tasted like lemon tea.
Next morning, I headed east, first through a bamboo forest and then out along the eight-lane Shenzhuan Highway. The road was lined with housing estates under construction, with vast homes, like Brookside on steroids. A sign read: Shanghai city centre 35km (22 miles).
I passed under one of the city's ring roads. Shanghai has three and will add more as the city grows, so that future historians will be able to judge the growth of it by these concentric circles, like a tree. It felt as if I had crossed the threshold into Shanghai proper. There were pavements and – joy – street signs with English translations. I passed Brobdingnagian factories – Shanghai accounts for a third of all China's exports – and an Ikea distribution centre the size of which might prompt a rethink about the Great Wall being the only man-made object visible from space. I walked under road junctions being built, tangles of concrete in the sky, and over railway lines where high-speed trains with platypus-shaped noses flew by every few minutes. And everywhere, there were signs of the old ways, of life lived on the pavement: women played mahjong, and laughed, men played cards, smoking furiously, expressions as stern as Easter Island statues. I picked my way through men bashing and welding metal, vendors with watermelon and aubergines laid out on blankets, and washing strung across the pavement at head height, which led, on unguarded occasions, to a face-full of underwear. Many of the older people wore pyjamas – Miss Fang had told me that they reminded them of their Zhongshan, or Mao, suits.
That night I stayed in Qibao, another canal town. But, unlike Zhujiajiao, this one was under siege from cranes and a glittering new shopping mall. Out walking after dinner, I stumbled across a group of around 100 women who, in the gloaming, filled a square with exquisitely choreographed dancing, arms making great sweeps of the sky, moving as one, like a flock of murmurating birds.
The next day, my last, the buildings and apartment blocks started getting much taller, many with pagoda decorations on the rooftops. It was as if I'd traversed the foothills and entered the high mountains. Outside a hair salon – I've never seen so many in one city – a young man was addressing two rows of workers. They clapped, did a little cricket-bowling action, sang a song, and then all went back inside.
I was firmly into that delicious walking reverie now, lost yet untroubled, absorbing this curious world with no desire for answers, my feet carrying me on effortlessly. I walked through Longhua martyrs cemetery, a rare piece of green now, memorialising those who died in the cause of Chinese communism, leading up to victory in 1949. Many of the graves held fresh flowers. An old man did tai chi under the canopy of a cedar.
I ducked down a narrow alleyway of preserved shikumen houses, little stone-arched dwellings that were once ubiquitous in Shanghai but have now largely been demolished, and into the South Xizang Road bird and flower market, the air a thick fug of cigarette smoke and animals. Boxes of rabbits, rats and kittens filled the floor. On tables were glass tanks of turtles and giant frogs and huge lizards. Hundreds of delicate bamboo baubles hung from the walls. In each was a cicada, chirruping loudly and uselessly to another, destined to spend its short time in an apartment as a rural soundtrack to an urban life.
On a large table, men were jabbing slithers of bamboo into the mandibles of crickets, trying to gauge their spirit – for betting on cricket fights is one way to get a surreptitious gambling fix in a country where, on the mainland, it is illegal.
I wandered into the exquisite 16th-century Yuyuan Gardens, and walked its serpentine paths, through tunnels of jasmine, mimosa and magnolia – the city's flower – and past lakes churning with carp. A man stopped me and pointed to his family and his camera, which I reached for, but no, he wanted a picture of me with his family. They all held up their Vs, as the Chinese do. The photographer said something. The family replied and smiled. Miss Fang would later tell me it was probably, "Where's the money?" – the Chinese equivalent of "Say cheese" – to which the reply is always, "In the bank."
I walked across People's Square, Shanghai's municipal hub, with its modern Grand Theatre, whose transparent plastic walls and sweeping concave roof give it the appearance of a giant funky ashtray, and the Shanghai Museum, shaped like a saucepan complete with handle on the top. And then into the adjacent Renmin Park, where I sat in a bandstand with a dozen locals as an old man in a white waistcoat and a red tie played a haunting song on a zheng, a type of zither. The woman sitting next to me wiped a tear from her eye.
Above the treetops of Renmin Park, encircling the space, was another forest, of futuristic skyscrapers – it's said that during the 1990s, half the world's tower cranes were over Shanghai. One looked as if a giant UFO had landed on its roof, another like a praying mantis about to pounce, another like it might take off for the moon. They were beautiful, yet terrifying.
I saw a large group of middle-aged people browsing sheets of paper pinned to camellia bushes spouting vivid pink blooms. On each sheet was some writing and, on some, a photograph of a young man or woman. I assumed they were prayers for the dead, but actually they were prayers for the living, as a woman I found who spoke English explained.
"These are the parents of of unmarried boys and girls in their thirties looking for partners for their children," she said. "In China, it was always the parents who made the matches. These people have followed their children into the city from the countryside, desperate to get them married. To be over 30 and single is a source of great shame for the family. But in the city it is hard for young people to meet decent partners."
We had been surrounded by people, clutching sheets of paper. One woman spoke to me.
"What did she say?" I asked.
"She wants to know if you have your own apartment."
Dusk was falling when I met Miss Fang on the Nanjing Road – Shanghai's Oxford Street – as we had arranged. She seemed relieved and surprised that I had found my way back.
"Now that we know each other, you can call me Fang Fang," she said.
Fang Fang and I walked past old couples waltzing to Are You Lonesome Tonight?, weaved between the hawkers selling knock-off Louis Vuitton and Rolex, and past the shops selling the real things, and under a giant screen showing films of pandas and paddy fields. For the odd miraculous second, when the din abated, the plaintive sound of a songbird from a cage on a balcony would hang in the still air.
At the end of the Nanjing Road, the buildings seemed to part like curtains, and there was the Huangpu river and, beyond, Pudong, until 1990 a boggy swampland, but now packed tight with skyscrapers of every imaginable, and some unimaginable, shape and size – Shanghai's iconic and totemic billboard for the restlessness and energy that is modern China.
There was the neon Twiglet of the Pearl Tower; the World Financial Center, at nearly 500m, looking like a giant bottle opener; and the staggeringly beautiful Jin Mao Tower, like a cut-glass pagoda. The buildings started to pulse with light, flashing up giant hearts and teardrops and Tetris games 300m high. Behind us was the Bund, the waterfront of aristocratic Italian Renaissance and art deco buildings that sprang up at the start of the 20th century, the last commercial frenzy in the city. They seemed to seethe at the upstarts across the river.
As fireworks filled the sky, I thought about my three-day, 30-mile journey on foot from the 14th-century to Pudong. I would soon be on a 250mph Maglev train to get my flight, which would turn that distance into an eight-minute blur. I was tempted to walk to the airport, I really was.
• The trip was provided by On the Go Tours (020-7371 1113, onthegotours.com), which has a five-day Eye on Shanghai break from £349pp, including four nights' B&B in a hotel, tours, excursions, a Huangpu river cruise, entrance fees and transfers, but not flights. A private guide costs about £50 a day. Flights were provided by Virgin Atlantic (virgin-atlantic.com), which flies Heathrow-Shanghai from £556 return
