In the heart of Seoul: The South Korean capital has plenty of surprises for urban adventurers

"I want to show you something," said my guide. "It's very Korean, and a little bit strange. You'll probably think it's silly." We were walking, on an autumn evening that turned crisp after dusk fell on a bright and balmy day, down Isadong-gil. This is a crowded, traffic-free street in the centre of Seoul – or so you assume, until a rogue scooter or van shoots across your path. It leads through a retail gauntlet of high-quality and mostly affordable craft shops to Tapgol Park. Here, 15th-century stone pagodas commemorate the kings of the Joseon dynasty, who united the Korean peninsula after 1392 – which has plenty of resonances in 2012.

We'd already listened to the fluent English patter of the double-acts who run the wayside stalls that cook and sell the nutty traditional sweet called "dragon's beard".

I imagined some ritual in one of the tea-houses, hidden down alleyways just off the main drag. Instead, we turned off into a small courtyard that hosted a sort of mini-mall, and went upstairs. There, gaggles of shrieking teens (well, it was Saturday night) clustered around automatic photo booths. They seemed – by the extravagant period outfits hanging all around – to have been hijacked by a theatrical costumier. The deal is that you pay a few thousand won (the exchange rate runs at 1,800 to the pound), select your historical fancy-dress, and leave giggling over the evidence of how fine you'd look as – in my case – a 17th-century Korean nobleman.

Korea surprised me, not least in its civic sense of humour – quirky, surreal, sometimes raucous and often, yes, a bit silly. Laughter has helped its citizens ease their rapid passage from the war-wrecked wasteland of the 1950s to today's urban and ultra-modern "Asian tiger".

It is one of the qualities that takes the edge off the daily stress of Seoul. Take the cheap and efficient subway (and you should: a single ticket costs 60p, while maps in Roman as well as Korean script, aid the foreigner). Just before a train arrives in the station, a merry little fanfare plays. You enter the clean, comfortable carriage with a smile. London Underground, take note.

Less than 60 years ago, this was a flattened battleground. In 1953, an armistice halted the war that divided the nation and it still, technically, continues. Since then, South Korea's capital has mushroomed into a 10-million strong metropolis, the core of a wider conurbation double that size. Just a few kilometres beyond Seoul, meanwhile, North Korea under its new leader Kim Jong-un still languishes in nuclear-armed poverty. Although many young people seem to care little about the unification question, trippers flock to the Demilitarised Zone to gaze through telescopes at their deprived neighbour at the Odusan Unification Observatory – surely one of the world's weirdest tourist spots.

This year, the country's per-capita GDP will surpass the EU average of around US$30,000: an astonishing ascent. Given that breakneck growth, veterans of other Asian urban giants might expect to find in Seoul a smog-choked, high-rise hell of neon and concrete grey. And, if you want outlandish skyscrapers, swish retail complexes and nocturnal dazzle, the city will satisfy big-time.

For a splash of glitz, try the pedestrian streets around Myeongdong, where Japanese tourists on shopping trips snap up designer labels beneath corporate HQs.

To glimpse this tigerish Seoul at its proudest, take the cable car up Namsan ("southern mountain") at night, with an electric rainbow of signage spread below. Even that short trip will show you why Seoul feels different from its counterparts elsewhere. Namsan rises on its green tuft abruptly for 260 metres, right from the heart of the capital.

On a hilltop viewing platform, hundreds of couples have attached padlocks to the railings as a token of undying love. Having savoured this inner-city idyll (which comes with obligatory fast-food outlets and even a teddy-bear store), you may descend again through trees into the metropolitan hubbub on an emission-free electric bus, for a lordly 30p.

Seoul feels cleaner, and greener, than many east-Asian rivals. Through autumn or spring, you may breathe freely and walk briskly – humid July or August would tell another story, which is why the 1988 Olympics were deferred until late September.

Some enlightened urban planning has – belatedly, perhaps – begun to mitigate the effects of the growth spurt: in the cleaned-up and now fishable Cheonggyecheon urban waterway, lined with paths and plants, that cuts through the heart of downtown, or in the cycle tracks that run along the broad Hangang – Seoul's Thames or Seine. You can hire bikes for a riverside spin, stop for a snack at one of the stylish cafés at the ends of bridges.

Hilly parks dot the suburbs south of the Hangang, the preserve of Seoul's richer half. But it's in the north-of-the river quarters, where most visitors congregate, that the paradoxical pleasures of "green Seoul" can be most easily enjoyed. Immediately north of the business and consumer hub, wooded mountains topped with rocky outcrops soar into the sky, a dream-like landscape transplanted from some antique scroll. Wild and dramatic scenery rears over the hooting, throbbing centre: rare in any sprawling city but, in booming Asia, surely unique.

Between the skyscrapers and mountainsides lies the green oasis of the palace district. Of the six royal residences, Gyeongbokgung is the largest and most varied, Changdeokgung is the most sumptuously designed and Changgyeonggung is, perhaps, the most peaceful.

Here, in the far-flung estates of the Joseon monarchs – first constructed in the 15th and 16th centuries, now immaculately restored – finely carved audience halls and living quarters, temples and pavilions, nestle amid gardens landscaped with a painter's eye.

In autumn, as the leaves turn to a dozen reds and golds, take the "secret garden" tour at Changdeokgung and you will feel like you've slipped into the decoration on a screen, or the pattern on a plate. Among the stars in this arboricultural heaven are ancient Chinese scholar and gooseberry trees, and venerable mulberries. One juniper dates back to 1250.

The Bukchon neighbourhood, squeezed between a couple of palace compounds, is an urban village noted for its one-storey hanok houses, each built around a small courtyard. Its survival, across the road from the downtown frenzy, shows not only that many citizens of Seoul seek to preserve tradition in the face of galloping development, but that they can wield enough civic muscle to prevail. Thanks to a long campaign by residents, Bukchon remains a delightful low-rise warren for wandering in narrow lanes, eating at Korean restaurants (shoes off, legs crossed) and browsing in the art galleries that have sprung up across the area. It also offers quiet homestay accommodation in hanoks. For the equivalent of £33 per night, I unrolled a mat on the floor, a stone's throw from the Changdeokgung palace walls.

At the western edge of Bukchon, tree-lined Samcheongdonggil rises past galleries and cafés through Seoul's version of Soho or Chelsea. Stop along the way, with the city's trend-surfers, for a good coffee or a glass of wine (pricey, like everywhere in Asia).

Then head into Samcheong Park, which is steep and forested and serves as a kind of taster for the Bugaksan and Inwangsan mountains, both of which peer down into the city from 350-metre peaks. A little further north, for stalwart hikers, lie the trails of the Bukhansan National Park.

Imagine if Hampstead Heath or Arthur's Seat grew overnight into the Peak District or the Grampians, and you will begin to grasp how spectacular, and special, is Seoul's highland hinterland.

With more huffing and puffing than one might wish for after ambling through an arty quarter, I climbed through the trees to Prospect Point and looked down over the high-rise city. In the shadow of towers of corporate power, the curved, carved roofs of Gyeongbokgung recalled an era of less frenetic, if riskier, authority. At twilight on a day of gazebos, gardens and forests, I felt I could adopt the lifestyle of a Joseon-era aristocrat. After all (don't laugh) I have the photos to prove it.

Travel essentials: Seoul

Getting there

* Korean Air (020-7495 8641; koreanair.com) and Asiana Airlines (020-7304 9900; flyasiana.com) both fly daily non-stop from Heathrow to Seoul. Korean Air will start flights from Gatwick in April.

* Regent Holidays (0117 921 1771; regent-holidays.co.uk), has an eight-day Highlight of South Korea group tour from £1,290, excluding flights.

* On The Go Tours (020-7371 1113; onthegotours.com) has a week's "South Korean Express" tour from £1,099, excl flights.

More information

* visitkorea.or.kr