Many American cities now enjoy an amazing reversal of fortune.

Once hollowed-out shells mainly for those too poor to move or those so rich they didn’t have to deal with the poor cities are again filling up with educated and aspiring young people.

They are flooding into Chicago, Philadelphia, New York and other places once given up for dead. The influx of newcomers with money has raised housing prices and property taxes for many longtime residents, leading to social conflict.

Who belongs downtown?

The short answer is everybody. But the short answer is too short.

Consider Honolulu’s Kakaako neighborhood. Once a flat, low-strung area of auto repair shops, warehouses and some residents, it’s now become a real estate bonanza for shopping centers and high-rise condos. A master plan for development envisions perhaps 22 residential towers plus acres of retail and office space.

People already living there are wondering what’s going to happen to their views. Then there are the old Hawaiian burial grounds.

Considering the sad financial shape of so many urban downtowns, such cities would be insane to turn away all those tax dollars. But there’s also a price to pay for the loss of modest neighborhoods inhabited by the same folks for generations.

One is fairness. Often, the most coveted areas are not the impoverished slums but those blue-collar holdouts where longtime residents and shopkeepers preserved the charming streetscapes. These people hung in through the bad old days of crime and filth. They’re still in the same little house, but now the value of the house has tripled along with their real estate taxes. Sure, some could sell at a handsome profit, but others call their surroundings home and want to stay.

Though many recent arrivals love the old buildings, they seem to prefer the new high-rise condos with granite kitchen counters. The residential towers replace the warehouses that employed the locals, take away the views and bring in chain stores salivating over the arrival of big spenders.

Even the small hip stores price out the old-timers. Where there was spaghetti and meatballs, there’s now artisan pizza. Handmade chocolate is nice, but for many residents, the hardware store was even nicer.

This process has been called Brooklynization. That refers to the transformation of gritty old Brooklyn neighborhoods into pricey hangouts best afforded by tech and financial types.

San Francisco, in particular, has become a hotbed of tension between the longtime bohemian types and an inflow of technology workers, thousands of them millionaires, many of them "entitled."

Again, urban America desperately needs these taxpayers, but it must recognize that cities have a fragile culture that big-money development can flatten. Balance must be found.

Everyone belongs downtown with one exception. That is rich foreigners using prime American real estate to park their money. Even they can be downtown, but cities should stop letting developers put up billionaire residential towers on prime real estate prime because the city’s residents, shoppers and workers made it so.

New York’s hallowed West 57th Street is now being lined by narrow needles, 50 or more stories high, with apartments going for $20 million, $50 million, $80 million. They are being marketed to filthy-rich Russians, Chinese and others looking for a safe place to "invest" their money. Typically, the buildings are more than half-empty most of the time.

We can understand former Mayor Michael Bloom-berg’s wish to bring in tax- payers ripe for milking, but there’s such a thing as selling one’s soul. And soul is an established city’s greatest asset. Once that’s gone, the place loses the very thing that attracted newcomers in the first place.

So who belongs in the city? Its people.

Froma Harrop is a columnist with the Creators Syndicate.