So amazing, in fact, that you sometimes suspect that the construction of New York has been a post-historical event. Don't worry. Swathes of Manhattan already resemble a museum-piece - a 1930s art-deco vision of the future, struggling manfully with Dickensian shades. It is a city which, in 11 months' time, will be an icon of the last century. The much more phenomenal growth of places like Shanghai's Pudong district in the 1990s makes Manhattan look as eternal as Rome or Damascus. A City That Time Forgot, so to speak.
The search for ancient history in Manhattan took me into the Lower East Side, to number 97 Orchard Street to be precise. In these ugly old streets lurks a strange paradox: of the many millions of immigrants who poured on to the North American continent in the latter half of the 19th century - bold, enterprising pioneers every one of them - an extraordinary proportion never got any further than a mile from their point of landing.
The effort of crossing the Atlantic? A residual magnetic pull from the Old World? Whatever it was that stifled their pioneering urges, the much- vaunted lure of the New World (spreading for thousands of miles to the north, south and west) was not enough to prevent millions of brand new immigrants from plonking themselves down and refusing to budge the minute they had landed. It is no surprise to learn that the Lower East Side of Manhattan quickly became the most densely populated urban area on earth.
The grotty brick-built tenement block at 97 Orchard Street was just the kind of place where most of these people ended up living. Between 1863 and 1935 this six-storey building - with four flats on each floor - housed up to 10,000 different people. Left derelict from 1935 (when changes in the housing law rendered it illegally dangerous) this particular house - one of many possibles - was bought up by the local authority in 1988 and it has since been converted into one of New York's most fascinating small museums.
The identities of the original occupants of the house have been researched in detail (with help from living descendants), and three of the flats have been restored in immaculate detail - to three particular moments in history. Three snap-shots from the century of immigration. There is the flat in 1874 of Nathalie Gumpertz, a German-Jewish dressmaker; there are the Rogarshevskys, an Orthodox Jewish family from Lithuania, in 1918; and there are the Catholic Baldizzis from Sicily in the 1930s.
Our tour guide, Amy Caroll, a graduate historian, was probably the most intelligent, interesting and well-informed guide I have ever encountered in any museum in the world - though maybe that's New York for you. The group comprised middle-class Americans from Chicago, Philadelphia and upstate New York - all come to gawp in astonishment at the squalor in which their compatriots have sometimes had to live.
Back in the 1860s the privy was in the back yard, there was one water pump, there was no trash collection and 20 families lived and cooked in a building not much bigger than a large townhouse. We poked about the dark hallway, noticing improbable bucolic scenes painted on to the wallpaper (which was in fact lacquered sacking, stuck to the plaster).
Over the years landlords were forced by law to make improvements. Minimal fire escapes became mandatory in 1867 - though the massive metallic stairway attached for the benefit of tourists in the 1990s puts those flimsy balconies into perspective. Running water and internal toilets arrived around the turn of the century. Shortly before the end, there was even gas and electricity.
But the delight of each apartment lies in the details. Take the relatively bourgeois Victorian rooms of Nathalie Gumpertz on the first floor, for example. We know that she, her husband, Julius, and two daughters arrived in the 1860s. We have her photograph. We know that her husband suddenly disappeared for ever in 1874 during a period of economic hardship. We know that she worked as a seamstress, that she had roses on her wall (found under 22 layers of wallpaper), stencils on the ceiling and lace in the windows. We know that she eventually became rather prosperous and was able to move up-town.
The Baldizzis, on the other hand, living here in the 1930s, looked resolutely 20th century. Photographs of Adolpho and Rosaria show them grimacing into the camera. They had luxuries such as (cold) taps in the sink, linoleum on the kitchen floor and an electric stove, beside which Mr Baldizzi used to sit chain smoking and listening to Franklin D Roosevelt's speeches on the radio.
Meanwhile, the middle-class tourist from Chicago could not believe that anyone had ever had to fill their own gas-meter with coins. I ruminated about the conditions in which the people of Shanghai - city of the 21st century - live today. Rather less well than the Baldizzis, presumably. But perhaps that is the cost of living in cities which are icons of their century. JA