A VISITOR returning here for the first time since the Berlin Wall came down has a moment of recognition on the S-Bahn, the elevated railway, while heading from Zoo Station east into the city center. As the train rumbles along, one suddenly notices a wide open strip.
"Isn't that unusual - a big vacant lot right in the middle of the city?" one thinks, and then the realization dawns: This is where the hated Wall used to be. Only a few years ago we would have had to stop, show passports, pay in hard currency to cross into the east.
The irony has been even sweeter over the past several weeks because of a splendidly tacky American circus ("Smash hit! Held over!") set up on the site of the former "death strip," where the hated VoPos - People's Police - once patrolled with their guns and their binoculars.
But this part of Berlin, the Potsdamer Platz, just east of the wall along the main east-west axis of the city, is of keen interest now to more than just children looking for the excitement of three rings under a big top. Before the war, locals took pride in this square as the busiest intersection in Europe. Now that it is going to be rebuilt, it has been the focus of attention of architects from around the world as they have competed for the right to design the new Potsdamer Platz.
The German-born American architect Helmut Jahn has just won a competition for the new complex that Sony is building there. Renzo Piano, known for his futuristic Centre Pompidou in Paris, has just won a competition for design of the new Daimler-Benz complex.
Not far away, at the Friedrichstrasse railway station area, the cornerstone has just been laid for another complex of three new major buildings. Philip Johnson, another world-class architect, has been awarded the commission for the new American Business Center to be built at Checkpoint Charlie, once a major crossover point between eastern and western sectors of the city. The reconstruction is also to include a Berlin Wall memorial.
It is not only the old eastern sector of the city that is making Berlin "the biggest construction site in Europe" after 1993, as Mayor Eberhard Diepgen put it recently. On the western side of the Brandenburg Gate and the old wall, the plan to refurbish the Reichstag, the old prewar parliament, for use by the Bundestag, and to relocate the chancellor's office and three or four ministries from Bonn is yielding another bonanza for architects. Central city crossings
And yet however much central Berlin may appear an architect's dream, Ulrike Plewnia, spokeswoman for the city planning department, stresses "We're not having to reinvent the city; the structure is already there."
She cites the S-Bahn, which runs basically a circle route around the city, in contrast with the U-Bahn, the underground trains, whose lines run generally east-west or north-south. When the S-Bahn was built earlier in the century, "it was quite an undertaking." Now, as the government of Berlin, which is in effect a city-state, is trying to encourage economic development away from the traditional centers of the Kurfurstendamm in the old western sector and Alexanderplatz in the east, the S-Bahn is coming in to play. The city has identified four "crossings" north, south, east, and west of the city center, where S-Bahn lines intersect with the U-Bahn, at which to encourage development.
Like city planning departments everywhere, Berlin's is striving to balance public and private interests in all these reconstruction projects.
Despite its architect's avant-garde reputation, the Piano project has won acclaim for conceiving of the area more as a traditional neighborhood, a recognizable public place that works together as a whole, rather than a collection of private structures that don't relate well one to another.
The city is striving to have housing included in the new Potsdamer Platz complexes, even though the private "construction lords" (as the German term translates literally) tend to prefer to build more profitable office and retail quarters. The city is also trying to encourage public transportation instead of private cars: The goal is for 80 percent of those coming into the area to use public transportation.
But the question, says Ms. Plewnia, is "How far can you really push investors? Berlin is still not the economic center of Europe, of Germany. We have certain firms' views on how the city should be rebuilt, but we shouldn't offend investors by making too many demands."
Meanwhile, over at the city transportation department, spokesman Tomas Spahn warns of impending traffic implosion early in the next century if some solution to the problem of crosstown traffic is not found. The new government quarter is to be established in a central location, naturally, rather than out in the suburbs, but can't for security reasons be on a main traffic artery.
The Christian Democrats, senior partners in the city government's coalition, are therefore favoring a plan to route crosstown traffic through the Brandenburg Gate and to widen the Leipziger Strasse. The Social Democrats, junior coalition partners, are leery of encouraging too much auto traffic, and favor closing the gate to traffic, narrowing the Leipziger Strasse, and routing cars along the Invalidenstrasse, which the Christian Democrats feel is too far north to be a good east-west connector. Railroad recontruction
For the public transportation system, reunification has meant a general refurbishing of lines once controlled by different sectors. "On most of the lines, there are old rails that need replacement. But at least we don't have to build new tunnels," says Mr. Spahn. One of the oldest U-Bahn lines, from Alexanderplatz to Mohrenstrasse, is being extended to the old western sector. Closed stations have been reopened, and the general timetable for the system has expanded from the size of a slender paperback to something more on the order of a computer manual.
Also on Berlin's transportation agenda is a new airport: Three sites are under consideration in Brandenburg, south of Berlin. Especially after the Amsterdam air disaster last month, Berliners are concerned about the amount of air traffic in and out of Tegel and Tempelhof, West Berlin's two airports.
But within a reunified Germany, air transport should be less important if railroads can be improved sufficiently. The former East German state railways basically inherited tracks from the Hitler period and didn't do much to improve them, says Spahn. As a result, many rail journeys take much longer than they should: From Hamburg to Berlin, for instance, is typically a 3 1/2- hour trip, and sometimes much longer, instead of 90 minutes, as would be the case over high-speed rails. With improved connections t o Warsaw, Prague, and Ukraine as well as western Germany, many passengers would travel by rail instead of by air, according to Spahn.