Once, not long ago, it stalked through a forbidding strip of wasteland, a harsh and ugly symbol of a divided world. Now it is a fast-fading memory, its remnants few and far between. They stand - where they stand at all - as curious anachronisms.
Follow the path of the Berlin Wall through the city center, and you learn a lot about Germany's once and future capital from what you see. And even more from what you don't.
Their eyes fixed on Berlin's baptism next year as the capital of a reunified Germany, the city fathers have launched into a frenzy of construction. And it seems no accident that much of this activity has obliterated the past, altering the geography of entire districts in ways that do not merely eradicate the wall, which was knocked down in 1989, but make it unimaginable.
This is not universally popular.
At the Checkpoint Charlie museum, for example, where for 35 years Rainer Hildebrandt has run an exhibition about the wall at its most famous crossing point, the wholesale destruction is viewed very dimly.
"Until 1989 we were fighting against the wall, and now we are having to fight to keep some of it" to keep memories alive, comments Hans Jurgen Dyck, one of Mr. Hildebrandt's aides wryly.
In its day, the Berlin Wall was a fearsome object, running a total of 97 miles and not just dividing the west of the city from the east, but hemming in the whole of West Berlin, an enclave within Communist-held East Germany.
Nor was it simply one wall. The 11-foot-high wall visible from the west hid a dead zone patrolled by dogs, a lower secondary wall, an antivehicle ditch, barbed wire, and electrified fences. Watchtowers and bunkers studded its length, and trip wires set off self-activating machine guns pre-targeted to cut down would-be escapees.
The museum documents all this well. But step outside, look down Friedrichstrasse into the former East Berlin, and you are in a different world from the museum's grainy black-and-white photographs. Where squat border-guard offices once dotted the wasteland among tangles of barbed wire and tank traps, now bright concrete, steel- and glass-plated office blocks fill the view.
"Halt! Construction in progress" reads an advertising billboard, which continues:
"1961: Erection of the wall.
1994-1998: One of Europe's most attractive business centers under construction."
If you turn left down Zimmerstrasse to follow the route that the wall used to take, and look closely at the buildings on the north side of the street in the old "Soviet sector," you can still see the iron pegs driven into the wall that were used to help seal the windows. For in many places in the city, the front walls of apartment blocks were simply transformed into "the wall" itself.
And then, almost hidden behind a row of young trees, you come across an intact stretch of the wall. Ironically, the wall that once fenced in a whole people is now fenced in itself - to protect it from souvenir hunters.
"Here stands the last remaining stretch of wall in Stadtmitte" district, reads a sign, "which did not have to make way for construction interests, but which has been chipped away."
In another irony, this 200-yard stretch has been preserved only because it stands directly above a testament to another German horror, recently excavated: the cellars of Nazi Gestapo Headquarters.
$5 billion facelift
For a hundred yards or so, the line of the former wall is traced along the curbside by a brass strip, which turns into red asphalt and then to fading paint. The line disappears altogether as you run slap bang into Potsdamer Platz, the largest construction site in Europe.
Potsdamer Platz was once known as the busiest crossroads in Europe (it is said that the Continent's first traffic lights were installed here) but after the wall went up through the middle of the square it decayed into an empty expanse of weedy nothingness.
Now the square no longer exists - it is filled with an astonishing conglomeration of half-built skyscrapers covering 30 football fields - an urban jungle of girders, raw concrete, plate glass, and mud where the noise of bulldozers bulling, piledrivers piling, and cement mixers mixing is deafening.
Potsdamer Platz, a $5 billion project, is the city's bluntest effort to turn its back on its past. If all goes according to plan, when it is finished by the year 2000 it will constitute Berlin's new heart. No longer will there be, as today, a "center West" and a "center East."
But what else will stand in the center of Germany's new capital is unclear. Emerge from the crane-spiked mess of Potsdamer Platz and walk north along the wall's old line, and a huge space to your right still lies empty, behind a wooden fence three blocks long.
It is the site set aside for a Holocaust memorial. But the project has been dogged by controversy, with some leading Berliners opposing the idea of a memorial at all, others objecting to its size and location, and others to its design. So nothing has been built, and nothing looks likely to be built in the foreseeable future.
Not that the area is short of landmarks. The putative Holocaust memorial site is bordered by the Brandenburg Gate, which used to stand in imposing isolation in the dead zone between East and West, the symbol of Germany's division.
Awaiting new purpose
It was here that President John F. Kennedy famously declared, "Ich bin ein Berliner," and here too that President Ronald Reagan in 1987 demanded of the then-Soviet leader, "Mr. Gorbachev, tear down this wall!"
Now, with traffic driving routinely between its arches, the Brandenburg Gate is somehow diminished, deprived of its old purpose in life, and still waiting for a new one.
From here, as you walk north, only old maps give any indication that the wall ran this way, and soon you cannot proceed anyway because the road in front of the Reichstag is closed.
That is because the Reichstag, a monumental piece of Prussian grandeur now capped incongruously by a steel-ribbed glass dome, is being refurbished to house the German parliament for the first time in some 60 years. For almost a mile around, workers are erecting offices for the future deputies and digging the cavernous entrances to road and rail tunnels that will run beneath the city center.
After picking your way around a lengthy detour, you can find your way back to the wall's old path at the Invaliden Strasse bridge over a canal that marked the border. An inconspicuous granite pillar, inscribed simply "Grenzubergang 1961-1989," recalls that this was one of the authorized crossing points during the cold war.
Otherwise, you would never know. The sloping canal bank on the old Soviet side has been planted with a grassy lawn, bushes, and trees - an urban pastoral scene dotted with parents playing with their children and old people sitting on park benches in the afternoon sun.
And where the border turned East, along Boyen Strasse, more young trees and grass disguise the strip of land that lay behind the wall. If you don't know why this stretch of open land breaks the pattern of streets and apartment blocks, nothing is there to enlighten you.
Perhaps this is not surprising; for local residents on both sides, the destruction of their neighborhood - socially and physically - was a trauma nobody cares to remember,. and for Germans everywhere, not only in Berlin, the wall symbolized their painful division.
Indeed, They are still struggling to overcome its legacy: After two generations of living in different countries, east and west Germans still do not understand each other.
A dramatic history
Memories are rekindled, though, at Bernauer Strasse, scene of some of the most dramatic escapes during the first few days after the wall's construction, where the street was in West Berlin but the houses that fronted the sidewalk were in the East.
As East German soldiers arrived to block up the windows, residents threw their children from fourth-story window ledges into stretched blankets and then jumped after them.
Today, Bernauer Strasse is the site of the only official memorial to the wall erected in Berlin.
A hundred-yard stretch of the original wall - painted gray to hide the graffiti that had accumulated over the decades - is set off between two towering steel barriers that bisect it at either end.
It was opened in August this year. Already, it has been defaced by spray-painted graffiti. To today's Berliners, the wall is just another flat surface.