The first thing that strikes you about Hong Kong in late May is the humid­i­ty. As I stepped out of the air-con­di­tioned hotel bus, my glass­es instant­ly steamed up. It was like walk­ing into a sauna. The air was tan­gi­ble: thick and moist. In this cli­mate you soon appre­ci­ate the ele­vat­ed walk­ways in cen­tral Hong Kong – so much cool­er than the streets filled with cars and bus­es.

The pedes­tri­an esca­la­tor, which takes you up the steep, low­er slopes of Vic­to­ria Peak, is a high-tech exten­sion of these. All you have to do is stand still while you are con­veyed through Hong Kong’s sticky air above the city’s busy streets. At some 800 metres, it is appar­ent­ly the longest of its kind in the world. Futur­ists like HG Wells and Jules Verne imag­ined that sky­walks and trav­e­la­tors would one day be ubiq­ui­tous in cities. They were wrong, but the cli­mate, geog­ra­phy and wealth of Hong Kong has made them a real­i­ty here.

Even in this age of megac­i­ties, Hong Kong’s sky­line at night is awe-inspir­ing. There is beau­ty in its audac­i­ty and ambi­tion. The glit­ter­ing cathe­drals of com­merce, their lights undimmed by the glob­al reces­sion, tow­er above the har­bour. Unfor­tu­nate­ly, the gaudy green lasers that blaze out from the high­est pin­na­cles threat­ened to reduce the whole cityscape to the back­drop of some 1980s pop video. All it lacked was dry ice.

Hong Kong is a ver­ti­cal city: it has more high-rise build­ings than any oth­er city. It’s only when you notice the old colo­nial build­ings that you real­ly grasp the scale of the place. Today, the tow­ers of the cen­tral busi­ness dis­trict dwarf the LEGCO Build­ing (built in 1898) on Stat­ue Square, once the heart of the city. (You can see an old pho­to of what the square used to look like here.)

Hong Kong has not tired of reach­ing for the skies. Opened this year, the Inter­na­tion­al Com­merce Cen­tre has become Hong Kong’s tallest build­ing, soar­ing 484 metres (1,588 feet) above Kowloon. The Ritz-Carl­ton Hotel on floors 102 to 108 is now said to be the world’s high­est hotel.

Like every tourist, I made the pil­grim­age up the Peak. Despite the cloudy weath­er, the view was indeed mem­o­rable. Look­ing down from the 550-metre Peak, you can see how Hong Kong’s sky­scrap­ers are hemmed in by the sea on one side and by dense for­est on the oth­er, a con­cen­trat­ed rib­bon of con­struc­tion. They had no choice but to colonise that extra dimen­sion of space above them. And beyond Hong Kong, lost some­where in the mist and the smog, was the main­land – the vast­ness of Chi­na.

Equal­ly mem­o­rable was the hair-rais­ing jour­ney up to the Peak, along a pre­cip­i­tous, wind­ing road on top of a sway­ing dou­ble-deck­er bus. Hong Kong is also served – rather more sedate­ly – by a won­der­ful sys­tem of old dou­ble-deck­er trams, which start­ed run­ning in 1904. I have read that they are the last oper­a­tional dou­ble-deck­ers in the world.

Anoth­er rem­nant from the past are the island’s last gas lamps (two-light Rochester mod­els) which still illu­mi­nate the Dud­dell Street Steps, a reminder of an age before elec­tric­i­ty, before today’s wired, glob­al cities.

But this is a city that doesn’t have much time for his­to­ry – unlike near­by Macau, whose six­teenth-cen­tu­ry cen­tre has been turned into a quaint but over-crowd­ed tourist Mec­ca.

One morn­ing, I took the Num­ber 1 bus north up Kowloon’s Nathan Street to the Kowloon Walled City Park. This was once one of the dens­est urban slums on the plan­et, home to more than 30,000 peo­ple.

The orig­i­nal walled city had been a Chi­nese gar­ri­son town. It remained Chi­nese even under the 1898 con­ven­tion by which the British gained con­trol of Hong Kong and Kowloon. It was an anom­aly, a walled com­mu­ni­ty out­side the juris­dic­tion of the colo­nial rulers. After World War II, refugees from main­land Chi­na cre­at­ed a shan­ty town here, beyond the reach of police­men or offi­cials. It became a self-reg­u­lat­ing city with­in a city. There was no elec­tric­i­ty or mains water sup­plies, so the resource­ful inhab­i­tants hijacked near­by pow­er cables and dug wells. They built rick­ety tow­ers up into the sky; every inch of space was pre­cious. In a city where there were no laws and no tax­es, crime and busi­ness flour­ished. It’s said that about 80% of Hong Kong’s fish balls were man­u­fac­tured in Kowloon Walled City.

Kowloon Walled City was even­tu­al­ly bull­dozed in 1993. Today, it has been turned into a tra­di­tion­al Chi­nese gar­den, a haven of trick­ling streams and care­ful­ly tend­ed plants. Ornate pavil­ions have been built where once ram­shackle ten­e­ment blocks stood (and some­times fell). Nar­row alleys lit by flu­o­res­cent tubes have been replaced by ser­pen­tine walks between clipped hedges. Now all that remains of Kowloon Walled City is a scale mod­el.

It’s June now and I’ve returned to a chilly, wet Eng­land. But my mind is still alive with mem­o­ries of this extra­or­di­nary city: busy food mar­kets sell­ing every kind of fruit, veg­eta­bles, fish, nuts, spices, dried mush­rooms and fresh­ly butchered meat;

tiny spe­cial­ist shops crammed with goods up to their ceil­ings, like an Aladdin’s cave;

vast mar­ble shop­ping malls in which the air is as cold as a mau­soleum (how many Pra­da shops can one city sup­port?); the sharp, jar­ring smells of sea­wa­ter and diesel fuel on the Star Fer­ry, cross­ing from Hong Kong island to Kowloon;

exquis­ite dim sum (my mouth is water­ing as I type this); nar­row streets like canyons, snaking between sky­scrap­ers; peo­ple prac­tic­ing Tai chi on the Kowloon water­front each morn­ing in a slow-motion bal­let;

an elder­ly woman push­ing a poo­dle in a pram at Hung Hom; tem­ples hazy with incense; the clank­ing of the trams on their met­al tracks in Cause­way Bay; bare-foot pil­grims chant­i­ng in front of the Big Bud­dha on Lan­tau Island.

One thing is cer­tain: I won’t for­get Hong Kong.

(You can watch a slideshow of my pho­tos of Hong Kong and Macau on Flickr.)