Satellite images have shown that Greater Tokyo, home to an astonishing 35 million people, is by far the biggest urban area on the planet.
The most amazing thing about it, say its many fans, is that it works.
Although Tokyo dwarfs the other top megacities of Mumbai, Mexico City, Sao Paulo and New York, it has less air pollution, noise, traffic jams, litter or crime, lots of green space and a humming public transport system.
American writer Donald Richie, who first came to Tokyo in 1947 and recently published the coffee table book "Tokyo Megacity", has dubbed Japan's massive capital and primary city the "livable megalopolis".
Many visitors marvel at the politeness and civility that, along with the nation's wealth, have helped Tokyo avoid the pitfalls of other big cities that have become polluted, noisy and dangerous urban nightmares.
Amid the neon-lit street canyons, thoroughfares for millions every day, small shrines and quaint neighbourhoods survive as oases of tranquility, largely shielded from blights such as graffiti and vandalism.
Writing for the Los Angeles Times, a correspondent recently celebrated the ballet-like choreography of up to 2,500 people moving across Shibuya's massive "scramble crossing" every time the pedestrian lights turn green.
In the fashion centre, and elsewhere in the pulsating megacity, "despite so much humanity inhabiting such a confined space, there's rarely a collision, sharp elbow, shoulder-brush or unkind word," wrote the correspondent, John M. Glionna.
On Tokyo's noodle bowl of subways, a rapid and efficient system with a smartcard pay system, most commuters respect rules of courtesy, switch their mobile phones to silent and take their rubbish home to recycle it.
Streets are rarely choked with cars because most city-dwellers don't have one, in part because they would have to own or rent a permanent parking space for it, in part because buses, trains or bicycles are viable alternatives.
Despite its best-in-class sense of order, Tokyo also has a buzz and a pulse, with cutting-edge and quirky youth fashion, design, architecture and cultural offerings that keep setting trends in Asia and beyond.
France's Michelin Guide has crowned Tokyo as the world's culinary capital, awarding it the highest number of stars, more than Paris.
Tokyo may have had its heyday when Japan was Asia's economic top dog in the 1980s and early 90s, but much of the look has survived -- as have the famously astronomical prices that keep scaring off many would-be visitors.
Japan's capital, where a watermelon can famously cost $20 or more, was the world's most expensive city for expatriates in 2010 with the exception of exorbitant Luanda in oil-rich Angola, according to consultancy Mercer.
On Mercer's Quality of Living Survey, Tokyo was number two in Asia after the city-state of Singapore -- but only number 40 worldwide, beaten mostly by smaller European and American cities, from Vienna to Vancouver.
However, trendy London-based current affairs, lifestyle and design magazine Monocle begs to differ -- last week it ranked post-March 11 disaster Tokyo as the ninth most livable city in the world , and a few years ago it placed it at number three.
"You just look at Tokyo and think it shouldn't work with so many people living together, but it does," said the magazine's Asia bureau chief Fiona Wilson. "It would be a problem everywhere else.
"It's not just the great trains. It goes beyond the functionality. It's the service, the food, the restaurants, the shopping. It's all great."
Another fan and Tokyoite, Colin Liddell, who writes for city magazine Metropolis, said the city works because of the "texture of Japanese culture", including a tendency to seek harmony not conflict.
"Ideas that would be seen as antithetical in the West can peacefully coexist in Japan," he said. "Someone in a mink coat may have no problems getting along with radical vegans and animal rights activists.
"It?s just a different intellectual ecosystem and concept of each other that magically defuses the conflicts we find unavoidable in the west."
Of course, not everyone loves Tokyo.
For some the endless city brings a sense of alienation and loneliness, captured, albeit from a foreigner's perspective, as the backdrop to the Sofia Coppola movie "Lost in Translation".
Many abhor the over-the-horizon sprawl that spreads across the Kanto plain and its often drab "Legoland"-style residential architecture.
Then there are the rivers and canals, including one at Tokyo's historic centre at Nihonbashi, that have been concreted and roofed by expressways.
There is a good reason for the drabness of much of Tokyo.
Over the past century, much of the city has been destroyed twice -- once in the 1923 Great Kanto Earthquake and again in the 1944-45 firebombings.
The March 11 earthquake and tsunami catastrophe that devastated northeast Japan once more badly rattled Tokyo, forcing hundreds of thousands to spend the night at work or walk home when the trains stopped.
The disaster, which caused several deaths, damaged buildings, emptied convenience stores and led to power outtages in Tokyo, also served as a reminder that the spectre of another "Big One" looms over the city.
This summer will be steamier than most for Tokyo's residents amid a power saving campaign that will see companies cut back on air-conditioning.
Love it or hate it, almost everyone marvels at the scale of Tokyo.
If it were a country, it would rank at about number 35 in population terms.
At the heart of it all is the Tokyo Metropolitan Government, which governs Tokyo proper with 13 million people from a skyscraper-scale town hall with a annual budget that, according to the Japan Times, equals Saudi Arabia's.
With over half the world's population now living in cities, Tokyo believes it has lessons for a crowded planet.
Last year Tokyo launched Asia's first carbon trading initiative, and the city government has pledged to cut Tokyo's greenhouse emissions by 25 percent by 2020 from 2000 levels.
Under a 10-year plan, Tokyo aims to create 1,000 hectares of new green area and plant one million roadside trees, improve air quality and aggressively push solar energy and hybrid and electric cars.