In the century of phenomenal change that just ended, no great city transformed itself--or was altered by outside forces--as often and as drastically as this once-again capital of Germany.

Berlin has been middle Europe's preeminent industrial powerhouse, a monarchist stronghold, a renowned hub of artistic achievement, the epicenter of a vicious totalitarian dictatorship, a city politically crippled by the first World War and physically flattened by the second, and later, simultaneously, the capital of a "satellite" communist state and an isolated outpost of Western resolve.

The strange state of existence that was the Cold War lasted longer than any of Berlin's other 20th-century incarnations, and since the fall of the infamous Wall in 1989 the city has been struggling mightily to remake itself yet again. This time it is a peaceful revolution--if you count as peaceful the daily jumble of jackhammers and rumble of trucks that come with living in a city-wide construction zone.

Expectations were--and are--high. Germany's best architects and, indeed, many of the best in the world were recruited to help design and plan new (or renovated) residences, roads, train tracks, rail stations (but no new airport, yet), electronic infrastructure, commercial buildings and government offices. The sheer volume of activity is exciting and impressive, and the speed of transformation in many districts is nothing short of astonishing.

No less remarkable are the breadth of the contentiousness and the depth of the divisions. Architecture and urban development are major topics of debate throughout Berlin. It seems almost as if every square meter of the sprawling city--Berlin covers seven times as much territory as Washington--has been bought, sold, discussed, designed, defended, attacked, redesigned and, ultimately, transformed.

The intensity of the arguments can be explained by the city's history and by the very speed of change. Also, the stakes are so high. Berlin is, again, in the fascinating process of becoming something else--and yet somehow remaining Berlin.

Concrete Symbols

It is hardly surprising that overt political architectural symbolism of any kind makes many Germans nervous.

After all, a certain notorious would-be architect--Adolf Hitler--believed in such symbolism so strongly that he was set to flatten much of Berlin in order to build Germania, his notion of a fitting seat for the Thousand-Year Reich. The architectural idiom was to be a swollen form of neoclassicism.

In reaction to this mania, official architecture in Bonn, the provincial city that became the capital of West Germany after World War II, developed along quiet, unassuming, abstract, modernist lines. Glass was important in the key Bonn buildings. The idea was, glass symbolizes the necessary openness of a democratic government.

But now the move of the capital back to Berlin has posed what author Michael Wise calls "an epic design challenge" in his book "Capital Dilemma: Germany's Search for a New Architecture of Democracy." The challenge was to find an architecture commensurate with united Germany's new status in the world, and yet in keeping with the principles of democracy.

The dilemma appears to have been resolved rather well.

Deciding to reuse the existing Reichstag building as the seat of the Bundestag, the powerful lower house of parliament, was an important first step. Architecturally, the 1894 building is a rather heavy-handed concoction of classical motifs and allegorical statuary. Its best feature, an iron-and-glass cupola, was blown off in World War II. But as a symbol of the continuity of democratic aspirations, the building had no competition.

To bring the building up to date, British architect Sir Norman Foster went through many designs before coming up with one that satisfied most of the politicians and, at the same time, met high aesthetic goals. It has a stunningly engineered glass-and-steel dome in the middle where the old cupola was.

Although open for only a few months now, Foster's dome already has proved its lasting value. With its spiraling ramps and excellent views, it has become a major tourist attraction and a first-rate metaphor for democracy--ordinary people walking every day above the legislators at work in the chamber below. (Views downward, however, understandably are screened.)

It is too early to judge with finality the second major piece of Berlin's new political cityscape--the "federal ribbon" under construction north of the Reichstag, with its centerpiece building for offices of the federal chancellor. But its promise is exceptional.

The concept is brilliant. An international design competition was held in 1992 for a site in the northern part of the Tiergarten formed by an oxbow bend in the Spree River. Berlin architect Axel Schultes, who placed first among 835 entries, proposed that the Chancellery and parliamentary offices be laid out in a broad east-west band spanning the Spree in two places.

Since one of the river crossings connected the former East and West, it was a bold move symbolizing reunification. Furthermore, the "ribbon" is an an architectural expression of Germany's parliamentary democracy, establishing a relationship between executive and legislature that is close and yet distinct.

Schultes then won a second competition to design the Chancellery building itself. (Different architects were selected for other buildings in the ribbon.) This design is now nearing completion. The building promises to be significant, striking and perhaps even strongly poetic--it is an immense, airy, white cube with powerful contrasts between solid and void, outside and inside. To temper its abstract monumentality, the architect designed a garden with high, wavy, free-standing columns in it, and atop each of the columns he intends to plant a tree.

Sadly, the ribbon is not being built in its entirety. In the east it halts abruptly at a low-lying apartment building that former East Berliners do not want to give up. The western end, where a chancellor's residence was supposed to go, remains empty. Most crucially, the "civic forum" in the middle is not being built--bigger than a normal city block, this is the great public gathering place that would help give meaning and human scale to the formidable ensemble.

The very force of the ribbon idea, however, may triumph in the end. As we in Washington have seen with Pierre L'Enfant's plan, a truly great idea has a way of fulfilling itself over time.

Signs of the Times

In the grassy median strip of a cross street off Karl-Marx-Allee in the former East Berlin stands a traffic signal with pictographs telling pedestrians when it is safe to walk, and when not. The "Don't Walk" image is a red human figure standing at attention, the "Walk" sign a casually striding figure in green.

On the far side of the street stands another traffic signal with a different set of images. The red "Don't Walk" figure has a strange, ovoid head and extends both arms sideways in an emphatic gesture, and the silhouetted "Walk" figure wears a tiny squared-off hat and steps jauntily forward, arm raised at the elbow.

In the parlance of the reunited nation the figure at attention and the bland walking man are identifiably western in origin--they're "Wessies." The figure with that bizarre egghead and the other with that crazy porkpie hat are recognizably eastern--"Ossies." A great hue and cry was raised when the Berlin government began replacing the eastern signals with those of western design, and the eastern design became a fixture in popular lore--the figures are still called Ampelmannchen--"little traffic signal people." The protests worked--in a way--and the replacements stopped.

Contrary to exuberant hopes after the Wall came down, the cultural, political, economic and social divisions between eastern and western Berlin remain strong. This situation is frequently referred to as "the wall in the mind" or "the invisible wall." But, as the juxtaposition of the two pairs of traffic images prosaically shows, those divisions also remain highly visible.

A Window on the Past

It happens frequently: A group of tourists forms a tight circle in the middle of Bebelplatz, a spacious, stone-paved square on Unter den Linden next to Berlin's opera house, and listens attentively to a guide.

After the group moves on, nothing can be seen that would have attracted such attention. That "nothing," however, turns out to be a rectangular opening in the paving, covered with strong glass. You look down into a room with a white floor and white, empty shelves. A nearby plaque informs you that the window marks the exact spot where, on May 10, 1933, Nazi students burned hundreds of books by the world's great thinkers.

Designed by Israeli sculptor Micha Ullman, this is one of the simplest and most eloquent of the many architectural and artistic efforts in Berlin to deal with the horrifying Nazi past.

Like all cities, Berlin is a palimpsest of personal and collective histories. In the act of tearing a building down, constructing a new road or building a new skyscraper--whenever you make any significant change--you are both encountering urban history and altering it.

Only Berlin, however, was the command center for the systematic slaughter of 6 million individuals because of their religion. For the most part the actual killings of Jews were done elsewhere, in camps at the end of railroad lines--but Berlin is where the key decisions of the Holocaust were made.

No issue has been more intensively debated during the rebuilding of Berlin than how to acknowledge the Holocaust and the Nazi past. The questions are of course many and complex, and are political and moral as well as aesthetic.

Can crimes on such a scale even be memorialized? If memorials are built, where should they be placed and precisely whom should they memorialize? What form should they take and how big should they be?

Such questions are difficult for many Germans to face, much less answer. It is hardly surprising, then, that the fate of a proposed national Memorial to the Murdered Jews of Europe remains undecided. A prominent site has been set aside and a design selected after much controversy--an undulating field of thousands of concrete stele designed by American architect Peter Eisenman and sculptor Richard Serra. Whether such a huge, heavy-handed memorial should actually be built in central Berlin remains a legitimate question.

The debate itself, however, has been healthy, and the past decade has seen many signs that Berliners are effectively and creatively engaging the shame and horror of the Nazi past.

One of these is the Topography of Terror, an exposed archaeological dig at the Wilhelmstrasse intersection that was the administrative center of Nazi terror--where Heinrich Himmler, Reinhard Heydrich and other top officials in the state security apparatus exercised their power. (A chilling German noun describes them--Schreibtischmorder, murderers at their desks.) Though a permanent building for this museum is under construction, is is doubtful that it will improve upon the cumulative power of the outdoor site.

Remembrances of the Holocaust are scattered throughout the city--signs at subway stations, simple memorial stones, elaborate sculptures. The gilded onion dome of the 19th-century New Synagogue is once again a feature on the Berlin skyline. Other important Jewish sites have been renovated. It is now possible in Berlin to get a feel for the presence of Jews in the city's history--and also to experience their absence.

The Wall

A stretch of the Berlin Wall still stands near the Bornholmerstrasse Bridge, where the first incredulous Easterners crossed unhindered into the West on Nov. 9, 1989.

This is one of the few surviving sections of the structure that formerly zigged and zagged through the city--more than just a wall. The concrete barrier was the edge of a wide swath of territory known as the "death strip" because of the people killed trying to cross it. Symbolically, the Wall was the city's grim defining landmark both to Berliners themselves and to the world at large.

And so the almost complete eradication of this massive scar from the Berlin cityscape is both surprising and confusing. A determined visitor can try to trace its path in the construction site that is central Berlin, but even with map in hand this is mainly a matter of eerie guesswork--the vacant lot here, the exposed sidewall there.

At the Bornholmerstrasse Bridge there is just a graffiti-covered relic, upstaged by billboards advertising cigarettes and shaving cream.

Potsdamer Platz

In terms of quantity and speed of change, Potsdamer Platz is without compare even in Berlin. Once Berlin's commercial hub, it was bombed to smithereens and then became part of no man's land when the wall was built in 1961. Just five or six years ago it was still an open field.

Today the place is packed with office workers, shoppers and entertainment-seekers despite the fact that it is not quite done. Actually it is no longer one single place but three disconnected, dissimilar large-scale projects developed by three big corporations. Each had its own ideas and, at a collective expenditure of $7 billion, each seems pretty much to have had its own way.

In the northwest stands a cluster of big, sleek, gray, steel-and-glass buildings designed by German-born, Chicago-based architect Helmut Jahn for the Sony Corp. as an office compound-cum-entertainment center. Despite Jahn's attempts to break down the scale--and despite a towering, superbly engineered tentlike roof for the central courtyard--the not-quite-finished complex seems rather soulless and dwarfing.

By contrast, on another large plot of ground in the southeast is a complex designed for the A+T Corp. chiefly by Italian architect Giorgio Grassi. The antithesis of Jahn's attempt to be original and daring, this row of conventional masonry buildings for apartments and offices looks as if it had been designed to put you to sleep. (One good point in all of the projects: The Berlin government was able to require that at least 20 percent of the construction be for apartments.)

Fortunately, sandwiched in between these two developments is a true heart for this instant urban center--a huge mixed-use complex developed by DaimlerChrysler.

Renzo Piano of Italy and Germany's Christoph Kohlbecker got the basics right in their competition-winning urban design concept for DaimlerChrysler. The project is divided into 18 separate buildings, most of manageable size. Attention to human scale is pervasive, especially at ground level. The conventional street grid contains slight angularities to keep things interesting. There are two excellent, and very different, exterior public spaces.

The developer-architect team also had the good sense to make sure that no single architectural sensibility dominate the project. Six different firms, including international stars such as Arata Isozaki, Richard Rogers and Jose Rafael Moneo, shared the commissions. Rogers's work here, in particular, is exceptional--he created three highly sculptural buildings that also are improbably light and airy.

On the other hand, Piano and Kohlbecker were able to insist that they receive the bulk of the work--the team designed eight buildings in all. In addition to ensuring a degree of overall unity, this automatically assured high architectural standards. Piano, the chief designer of the team, is a humanist and a technological perfectionist who here took in stride the challenges of working on a grand urban scale. The eight buildings are appropriately varied in shape and size, and there is a certain poetry in the crispness of their metal, glass and terra-cotta facades.

Thus, the center of the immense Potsdamer Platz project is an aesthetically pleasing, lively environment--even if its commercial core is nothing more than a shopping mall, even if the whole $7 billion development remains a bit unnerving. It is in Berlin, but it could be almost anywhere.

The Reconstructionists

Berlin was a home to outstanding modern architecture for most of the 20th century. It seems odd, then, that Berlin's architectural arguments during the '90s centered around a cautiously conservative doctrine called "critical reconstruction."

But that is what happened. The word "critical" refers to criticism of modern architecture and planning, and "reconstruction" to rebuilding Berlin on the basis of traditional, local urban patterns. Critical reconstruction, then, is similar in many ways to neo-traditional town planning (a k a "new urbanism") in the United States.

For much of the decade of the '90s, at a time when many of the crucial decisions about Berlin were being made, advocates of critical reconstruction occupied positions of great power. These decisions continue to shape the city and visions of its future. Hence the continued relevance of the question: Is critical reconstruction a good or a bad thing?

To a dispassionate outsider the answer is, a bit of both. It also depends a lot on where you look.

At the Hackeschen Hoefe in the former east, for instance, critical reconstruction seems a triumphant idea. This is a sequence of 19th-century buildings of the kind that still dominates inner-city districts both east and west. To many, such courtyard buildings are the very essence of traditional Berlin (never mind that they once were appalling slums called Mietskaserne--rental barracks). Renovated to something approaching their Jugendstil glory, the eight Hackeschen Hoefe buildings today hum with vibrant commercial and residential life--and the success has stimulated many similar projects.

This suggests that critical reconstruction is at its very best when the reconstructing is literal--that is, when it involves renovation rather than new building. But this isn't necessarily so. The late Italian architect Aldo Rossi took an entire block and transformed it with a vibrant, colorful, contemporary reinvention of the Berlin courtyard block.

Pariserplatz is a test case of a different sort. This famous plaza, directly east of the Brandenburg Gate and destroyed during the war, is being rebuilt with separate projects by eight different architects, all working under strict guidelines. Several architects interpreted the regulations as formulas for dull, featureless buildings or such exercises in nostalgia as the Adlon Hotel with its dormers and tacky mansard roof.

On the other hand, there is American Frank Gehry's DG Bank, due to open in February. Gehry turned the regulations inside out. The building faces the Platz with a severe minimalist facade, and then, on the inside, it goes absolutely bonkers. The sculptural object that surrounds conference rooms and cafeteria in the building's atrium, made of wood, glass and scaly steel, looks like a beautiful surrealistic mutant.

Friedrichstrasse is yet another key location--and here, too, results are uneven. This is a former commercial Main Street that became a rather dreary boulevard under the German Democratic Republic. The idea--a good one--was to return the street to its prewar dimensions and functions. But again the regulations appear to have been quite rigid, requiring long, low, boxy buildings (even lower and boxier than in height-limited Washington).

Quite a few notable architects flopped on this important street. American Henry Cobb of Pei Cobb Freed & Partners tried earnestly to enliven the long facades of his structure with projecting triangular bays--and ended up with a building that looks as if it were suffering a nervous breakdown. French star Jean Nouvel's block-long all-glass building with the curved corner smartly refers to '20s Berlin modernist Erich Mendelsohn, but it seems an empty gesture--the supposedly crystalline facade always looks dirty. And so on.

But again there are exceptions. German architect Oswald Matthias Ungers put together his obsessional square geometries with good materials and a good plan to make one of the Friedrichstrasse boxes into something with a certain low-key dignity. A few blocks away American David Childs of Skidmore, Owings & Merrill designed a satisfyingly urbane office building.

Some of the best architecture in Berlin is so good or so different (or both) that it seems outside of the general debate--Daniel Libeskind's extraordinary Jewish Museum Berlin, for instance, or Foster's Reichstag dome or (most likely) Schultes' Chancellery. Yet the verdict on critical reconstruction--and thus on much of the architecture of the new Berlin--is mixed.

This is perhaps inevitable, given the volume and speed of the building--and perhaps just a little bit sad. The overall quality is pretty high, but unlike, say, Barcelona at the end of the 19th century, Berlin did not develop a distinctive "Berlin" style at the end of the 20th century.

A Work in Progress

The bronze-tinted glass glints in the late afternoon sun, calling attention to the Palace of the Republic, one of the biggest, least attractive and most controversial buildings in all of Berlin.

Aesthetics is not the main issue. Symbolism is. The republic in this palace's name is that of the German Democratic Republic, the government that erected the building a quarter-century ago. Another palace once stood on the same prominent site--the Royal Palace of the Hohenzollern dynasty that for five centuries ruled Prussia, and then all of Germany, from Berlin.

Even before that dynasty, this place was important to Berlin. It was, in fact, the area where the city got its start in the late 12th century. Not much of the medieval city is left, but the quiet dignity of the early 19th-century neoclassical buildings and squares testifies to the ambition of Karl Friedrich Schinkel--still Berlin's most famous architect--to transform Berlin into "Athens on the Spree."

The privileges of Hohenzollern family were of course terminated after World War I and their former palace was severely damaged during World War II. The royal building was then finished off in 1950 on the orders of Communist Party chief Walter Ulbricht, who declared, "The center of our capital must become a grand square for demonstrations upon which our people's will for struggle and for progress can find expression."

When the Palace of the Republic finally went up in the early '70s, there was still plenty of room for parades and such, for as big as it is, the building does not come close to matching the size of the royal abode, which had 1,200 rooms and occupied all of what is now called the Schlossplatz (Castle Plaza). The GDR building takes up a mere third of that space.

This capsule history suggests the strengths of the emotions that the place and the palaces still arouse. The site is a primary locus of Berlin's complex history, and people project their own versions of that history onto both the land and the buildings. Little wonder, then, that the Palace of the Republic is the city's most visible and most intractable architectural standoff.

The big building may be ugly--it is a but a box sheathed in marble and glass--but it served, as historian Brian Ladd points out in his book "Ghosts of Berlin," as "a public place--and a decentralized, unhierarchical one." The East German parliament met inside, but mostly the building housed theaters, meeting rooms, bars, cafes and restaurants. There was even a bowling alley.

This high degree of public usage explains the outcry that greeted a 1993 decision to demolish the structure. Many easterners resented the elimination of a genuine meeting place. Many westerners, by contrast, resented the building as a communist monument, and these folks rallied around a proposal to rebuild the old Royal Palace.

Fortunately, this preposterous notion seems to have sunk of its own weight--who other than a monarchist would want to rebuild a royal palace in the heart of a democracy? By the same token, simply keeping the Palace of the Republic (currently closed and undergoing a lengthy asbestos removal procedure) is not a satisfying outcome. It is a sorry excuse for a civic building in one of the most important urban spaces in all of Germany.

Another way to look at the current standoff, however, is as a necessary pause. Berliners have been asked to do a lot in a mere 10 years--and they have done a lot. By a decade from now, perhaps, they will have found the consensus and the will to make this central space an enjoyable, beautiful, memorable meeting ground for all.