Manhattan is the only urban space that has tall buildings and a very active street life, in the same areas.
This is what makes it a "great city" — not its overall size, age, or wealth, or its monuments or its power or geographic position.
Just about every other city in the world with an active street life has low-rise buildings (take any old-world or latin American city.) There are, by now, many cities with high-rise buildings and street culture, but their exciting pedestrian action is located elsewhere in town (San Francisco, Chicago, New Orleans, Mexico City, Buenos Aires, Singapore, Shanghai, Frankfurt, Paris, etc.).
In New York City alone, a vibrant street life is truly framed by tall buildings, some very tall, but most just "tall," short by local standards and very high by international standards (15 to 40 stories) as well as completely normal size buildings (1 to 6 stories). And there are lots of these large buildings — it's not just a small area. All of midtown, parts of uptown and even the Village, and certainly the Wall Street district have so many tall buildings that most of them are anonymous, no one notices them or their desperate attempts at signifying wealth and status by alluding to ancient Greece or Rome, and Venice, Paris and London. Any one of them alone could be the star structure of any smaller city in the US.
I would like to emphasize the importance of "medium tall," as opposed to "sky scraper." Sky scrapers do little for cities except as icons, and only if they work visually from afar. They have very little of what I call "bottom life, " that is the street life that takes places in front of and because of them. "Medium tall" buildings, generate street life as effectively as any 19th century traditional building and are the secret to this exciting city, because there are many hundreds of them.
In Manhattan you are not just ON a street. You are IN a street, very much like in a medieval town. In New York, this social, vertical experience still exists, proportionally translated into our time. The tallness of structures doesn't seem to impede culture in New York. In every other city, as far as I know, the vibrancy of public space rapidly decreases in exact proportion to the height and modernity of its buildings. In New York, height actually creates social enthusiasm. In all other cities, height is felt as an expression of distance and arrogance.
But, in New York, too, the real cultural centers are in the shorter (older, nineteenth century) areas; so the pattern applies here as well, but less. New York's cultural ferment is so productive that it seems to elevate the high-rise zones, Wall Street and Midtown, to the point of being "alive" even at night.
I speculate that this may have to do with the fact that New York City has developed tall buildings — buildings that would require an elevator — much earlier than other cities. Height showed up in Manhattan before modernism (in the Bauhaus or internationalist sense). New York didn't just invent skyscrapers, it normalized "tallness" in the mixed-use urban environment. New Yorkers made tall buildings while people still knew how to create architecture that doesn't interrupt urban flow. New York had tall buildings with the sound of horses in the streets.
The obvious pattern is that the more a city contains nineteenth century (or earlier) construction, the more street life it has. New York is nineteenth century enough to be culturally functional while prospering in the twentieth century enough to maintain verticality.
