BERLIN -- "Berlin, more than almost any other great city, is a city of birds." So wrote Otto Friedrich in "Before the Deluge," the luminous portrait of Berlin in the 1920s that he published in 1972.

"One hears not only sparrows chirping in the midst of traffic on the Kürfurstendamm but wood thrushes singing in the Glienicker Park. One sees species one never expects to find in cities -- magpies and nightingales and a black-feathered, yellow-beaked diving grebe known as a 'water-chicken.' Even at the Hilton Hotel, the traveling businessman wakes to the sound of peacocks screeching in the night."

To which it only need be added, thirty years later, now that pollution in the former East Germany has been dramatically reduced, several varieties of herons are once again abundant around the city's many lakes as well.

Yet Berlin real estate today is among the greatest bargains in the world. The city is economically moribund. It lacks a single direct flight to any city in the United States.

Probably no major city is less dense, at least on an appropriate measure. Draw a circle around the city twenty five miles in diameter. Something like a quarter of greater Berlin's total area comprises great swathes of forest. Add to that the preservation of the countryside beyond, thanks to fifty years of slow East German growth (West Berlin, of course, was an island deep inside the communist East) and you've got a greenbelt a hundred miles wide. Pass through Potsdam in the south or Gatow in the west (the old British sector) and you are in the country.

Berlin is "a new city," said Mark Twain when he moved here with his family in 1891 to write a book, "The newest I have ever seen. Chicago would seem venerable beside it." (He moved back to America three years later.) Like the Windy City, Berlin grew rapidly during the second-half of the 19th century from a relatively small city to a great metropolis -- after its Prussian kings permitted Otto von Bismarck to unify Germany and turn them, however briefly, into emperors. (Kaiser Wilhelm II abdicated in the closing days of World War I and a republic was proclaimed.)

And like Chicago, Berlin owes its prominence to water. Located at the juncture of the Spree and Havel rivers, far to the east of the industrial valleys of the Ruhr and the Rhine, and well over a hundred miles from the nearest Baltic port, it was nevertheless an improbable exporter of heavy industrial goods to the rest of Germany and the world, for a hundred years. Virtually all of that business is gone now.

Twain continued, "... The next feature that strikes one is the spaciousness, the roominess of the city. There is no other city, in any country, whose streets are so generally wide.... Only parts of Chicago are stately and beautiful, whereas all of Berlin is stately and substantial, and it is not only in parts but uniformly beautiful."

Incredibly, not even the devastation of the Second World War changed that aspect of the city very much. Berlin is still beautiful, as much as can be any city located on an extensive plain. With its enormous central park, the Tiergarten, its leafy, sprawling neighborhoods and superb public transportation system, Berlin is thoroughly liveable, like the New York City of fifty years ago or the Toronto of today. Much of the Prussian splendor in its center survived or has been restored.

East Germany was absorbed into West Germany in 1990. The capital was returned to Berlin from Bonn in 1999. Since then, the Federal government has poured money into the city. Indeed, there is hardly a major architect in the world who hasn't built in Berlin. The city has three universities, three opera companies and dozens of museums -- none of them profitable, strictly speaking. The old Prussian summer capital of Potsdam, another tax sink, is only half an hour away by train.

Berlin, in short, is a city of vast amenity, on a par with London, Paris, Rome and New York. So far, low rents, high culture and the romance of Wim Wenders' 1987 classic Wings of Desire have produced mostly the bright kids the locals call "rucksackers." And it is fashionable to despair of the city's ability to ever again produce enough revenue to support itself. Comparisons to Washington D.C. and Brussels abound.

But if Jane Jacobs if right, Berlin possesses exactly those attributes that eventually will lead to its regeneration. Indeed, it is something of a test of her conviction that diversity plus history breeds growth. Berlin is a a city where smart people want to live. They will find ways to live here. And while it is always dangerous to predict the flow of technology -- last week I looked an extensive 1965 comparison of the space program to the rail system -- I have been struck by the work of one of the laboratories I had come to Berlin to see, the Institute for Theoretical Biology at Humboldt University.

Berlin, like Boston, is moving into brain science. One of the promising avenues of approach here has to do, curiously enough, with birdsong. Hardly a week passes without a talk by one researcher or another on the "nonlinear dynamics perspective" on birdsong or "Spectra and Waiting-Time Distributions in Firing Resonant and Non-Resonant Neurons." Last month Richard Hanloser of MIT was here to discuss "The generation of neural sequences in a songbird."

"Little is known about the biophysical and circuit mechanisms underlying the generation and learning of complex motor sequences," Hahnloser noted. But thanks to recently-developed microscale devices for monitoring the activity of single neurons in the brains of singing birds, "we are beginning to understand the circuits that generate complex vocal sequences." Where does it lead? Who knows? But at least some part of Berlin once again is at the forefront of a rapidly-advancing science, as it was in physics and quantum mechanics a hundred years ago.

True, Berlin has many obstacles to overcome, before the city again begins to throb with life and real estate values recover. Chief among those barriers is what Twain described in 1881 as "The Awful German Language." But then that barrier to entry can also turn out to be a protective shield.

This is the country that invented both the research university and industrial research and development, not to mention the Protestant ethic and much of the Welfare State. Yes, Nazism and firebombing and the Holocaust were invented here, too. Then in 1989, with the dismantling of the Berlin Wall, Germany reinvented itself. As the historian Robert Darnton has written, "The peaceful revolution of 1989 did not just free the Germans from the last vestiges of more than a half-century's dictatorial rule. It freed us from what we thought of them."

The generous terms upon which East Germany was merged into the Federal Republic were as far-sighted as the Marshall Plan that helped put Germany on its feet after World War II. The decision to move the capital to Berlin was equally far-sighted. It will take time to pay the bills. But in due course, plenty of smart people may be willing to learn German in order to live in a green leafy city with three opera companies where the loudest noise often is the chirping of the birds.