Start in Greece, on Danforth Avenue in the east of the city. In the half-dozen blocks between Pape and Logan Avenues, Greektown sets the tone for the city's neighbourhoods. A sprawl of suburbs suddenly bursts into life with street activity seemingly straight from Athens. And, as in the Greek capital, there are a few quiet hideaways such as the Ellas Dining Room, whose facade resembles a strictly Classical temple.
As you move west, the viaduct over the Don Valley Freeway gives you a first taste of America. Toronto sprawls for miles along the north shore of Lake Ontario, and occupies one of the few parts of Canada that dips below the 49th parallel. The United States' border is just 30 miles away across the water. Canada is too cute to be the US, but the strangle of roads and dazzle of highrises beyond shows a few pretensions on the part of its largest city.
Ireland is next: Cabbagetown began as a derisory nickname for the area in which immigrants from Kerry and Cork settled. Rather than waste the space in front of their modest Victorian homes, they grew vegetables. The area around Wellesley Street east of Parliament Street used to be the sort of place for which the term "inner-city decline" seemed designed, but now it is as cool as London's Camden Town. Step off the main drag to Wellesley Cottages to see how the present crop of Cabbagetown residents - including a harvest of media types - is doing.
To see how the other animals live, continue to the end of the road. To eliminate the risk that city-dwelling children could grow up without seeing a shred of the Canadian great outdoors, a small part of the country has been brought to Toronto - which is where you will find Germany. At Riverdale Farm, a huge Friesian barn has been imposed, with studiously plain lines and angles. The mosaic of colours in the schoolchildren visiting the farm demonstrates the Canadian tradition that their society is a salad bowl rather than a melting pot.
Though racial conflict is not unknown, Ontario has long been a liberal, tolerant haven; when slavery persisted south of the border, black slaves could find freedom and work in the province. One in five Canadians was born abroad, and wave after wave of immigrants have found a warmer welcome than they might have received elsewhere in the world. Most street names are staidly 19th-century: King and Queen, Church and College, Victoria and Albert, reflecting the Imperial outpost that Canada comprised at the time of its creation in 1867 (an event celebrated each 1 July with Canada Day, which just happens to be 72 hours ahead of US Independence).
Take a street car named Spadina across to a Seventies coalition: first the CN Tower (a snub to Chicago, and the tallest free-standing structure in the world - which means it's a television transmitter with attitude but no guy ropes); next, the Skydome, the next slice of Americana at the end of Blue Jay Way.
The street is named after Canada's most successful baseball team. The Blue Jays are almost always entertaining teams from the US. But, if you play in the American League, that is what you must expect. After a successful run, the Jays have hit hard times and are in danger of ending up near the foot of the table, becoming what the commentators call "cellar dwellers". But to share the excitement of fast play and American excess, spend just $6 (less than pounds 3) on one of the cheap seats.
The US-Canada border seems to function as a semi-permeable membrane, with only the more wholesome aspects of American life getting through to Canada. So you can enjoy the full-on popcorn-to-pitcher experience in the stadium - without fearing a mugger-to- murderer sequel when you leave at the end of the evening.
The most visible minority in Toronto is the Chinese community, whose present heartland occupies a high-energy splodge on Spadina Avenue between College Street and Grange Avenue. Commerce proceeds more frenetically than anywhere this side of Hong Kong, conducted mainly in Cantonese. In the constantly shifting cultural sands of Toronto, Vietnamese people are settling in a few of the gaps on Spadina. (For the biggest bowl of soup you ever did see, order the Special Beef dish at Pho Huong Viet at number 374, but you had better like tripe.)
Vietnamese businesses are occupying premises vacated by Chinese who have moved out to some of the more illustrious suburbs. In little more than a century, the Chinese have settled and uprooted several times: the very first immigrants arrived in 1878, though the site of their original community has long been buried beneath the city centre skyscrapers. More recent arrivals have established toe-holds among the low-rises on Kensington Avenue, straggling behind the Chinese quarter. Caribbean and Hispanic people predominate, until a few blocks later you collide with the Portuguese Village.
The epicentre is the corner of Dundas and Euclid, at the newly opened Medala restaurant. Here you discover that the entire Portuguese diaspora is covered, including sub-communities from the Azores, Macau and Brazil, and that the English language is not always effective. I ordered a glass of water, but - at two in the afternoon - received the equivalent of a treble vodka.
Honest Ed's Jewish village seemed a touch hazy after that. Ed Mirvish, the city's favourite entrepreneur (a kind of Richard Branson figure, but without the trains) has amassed a fortune from piling high and selling cheap, and has used some cash to support small businesses from the Jewish community. If you can get to Toronto by tomorrow, the quarter will be alive with free activities to celebrate Mr Mirvish's 80th birthday.
Recharge with the sharpest espresso in town, on the "Corsa Italia" (as the western part of Dundas Street is known). Just in case you failed to pick it up from the preponderance of pizzerias, coffee bars and beautiful people, the street signs announce you to be in Little Italy. In theory, you could eat in a different Toronto restaurant every night for 17 years; if you so did, you would end up spending a lot of time here. Beyond Italy, nations fragment. A Ukrainian church, a Peruvian restaurant, and an Eritrean cafe line your progress to the city's finest cultural totem, a structure magnificently mislocated: Casa Loma.
The translation, house on the hill, barely does it justice. "North America's largest castle", boats the tourist board. Never mind that there is not too much competition for this title; the achievement of eccentric tycoon Sir Henry Pellat was to create a majestic Scottish baronial hall in a leafy suburb of Toronto. If he had spared some expense in the building from 1911 to 1914, like importing Scots craftsmen to lend authenticity, he might not have had to endure the pain of seeing the whole place sold off to pay some of the massive debts he ran up in a Barings-style disaster.
Almost every asset in the place was stripped in the Twenties, but it is gradually being restored to its original divine madness. Anyone who asserts that Canada is a dull country should be dispatched here forthwith. Like Sir Henry, Toronto is the embodiment of good intentions. And it is the ideal city break for people who don't much like cities. But one question still nags in a nation that is officially bilingual: why, amid the ethnic spectrum, is there no French quarter?
Getting there: Simon Calder paid pounds 217 for a return charter flight from Gatwick to Toronto on Air Transat, booked through Quest Worldwide (0181 547 3322). Fares in August are rather higher.
Getting information: Visit Canada Centre, 62-65 Trafalgar Square, London WC2N 5DY (0891 715000).Getting the picture: the writer reports from southern Ontario for `The Travel Show' next Monday, 26 July, at 8.30pm on BBC2