WEST BERLIN -- Leni Riefenstahl, the German filmmaker whose "Triumph of the Will" chillingly captured the gripping emotional appeal of Adolf Hitler and the Nazis, has always claimed that she deified Hitler and his henchmen out of artistic naivete rather than political sympathy.

But here -- behind barbed wire, in a heavily guarded bunker at the dead end of a pretty street of villas and pine trees in the West Berlin suburb of Zehlendorf -- a telegram Riefenstahl sent to Hitler sits in a file.

The wire, written on the occasion of the Nazi invasion of France in 1940, says: "With indescribable joy, deeply moved and in fervent gratitude, we experience with you, my Fuehrer, your own and Germany's greatest victory, the arrival of German troops in Paris. . . . You are accomplishing feats that are unparalleled in the history of mankind."

The Riefenstahl telegram is one of about 100 million pieces of paper in 30 million files in a massive underground complex called the Berlin Documents Center.

Once the headquarters of the Gestapo's phone-tapping operation, the center is now American property, probably the world's largest and most valuable collection of materials documenting the Third Reich.

But with the two Germanys reuniting and the American role in Berlin about to be dramatically reduced, the documents center is destined to be handed over to the German government.

In the days after the German surrender, American soldiers found the records in caves in Germany and Austria and brought them to Berlin in armed convoys. The membership rolls of the Nazi Party were at a Bavarian paper mill, about to be pulped, when Americans saved the 11 million cards.

Ever since, the Berlin center has been an essential source for prosecutors, historians and writers chronicling the Third Reich, prosecuting Nazi war criminals and denazifying postwar Germany. Even today, the records -- party cards and personnel dossiers, so numerous that many have not yet been examined -- are in constant use, generating about 5,000 requests a month for information.

They helped confirm the death of Josef Mengele, the "Angel of Death" at the Auschwitz concentration camp. They have been used in the search for evidence that Austrian President Kurt Waldheim was involved in Nazi war crimes. They are still a primary source for the U.S. Justice Department's Nazi-hunting Office of Special Investigations.

"Not a single war crimes trial has been conducted without someone consulting our records," said David Marwell, the center's American director.

Prosecutors are by no means the only users. Minnesota researchers are combing through the party membership files to try to figure out what kind of Germans became Nazis and why. German scholars are looking at early party members and the references they gave, tracing the paths by which the Nazi movement expanded.

The West German government has used the documents to decide whether to grant citizenship to tens of thousands of East European refugees who claim to be Germans.

Deep in the basement here, sealed off from the files to prevent burglary or vandalism, German women sit at electronic consoles, methodically microfilming 40,000 sheets of paper a day.

A video surveillance system allows security staff to zoom in on the slightest finger movement of a microfilmer who might try to swipe a document. In the mid-1980s, an estimated 30,000 documents were stolen from the center, ending up in the hands of German memorabilia dealers who paid up to $3,000 per document.

In an adjoining room, Americans enter information from the documents into computers. After five years, when the microfilming is expected to be completed, the United States will keep the film; the Germans will get the originals.

The idea of putting Nazi documents back in German hands offends Jewish groups, which say they fear Germany might make it more difficult to prosecute war criminals or to conduct historical research.

The center should remain under U.S. control because "we paid for it the hard way, with the blood of American soldiers," said World Jewish Congress executive director Elan Steinberg.

A tour of the facility provides a window into the Nazi obsession with documentation.

Files full of half-century-old pink cards used to evaluate requests for German citizenship include an elaborate pseudo-scientific scale for determining Aryan characteristics. Examiners measured 21 physical features of an applicant, including "roundness of nose, height of nose, form of hair and fold of eyes."

An ethnic German living in Romania who was resettled in Germany in 1941 applied to become a citizen. Nazi bureaucrats recorded his physical characteristics, cataloged his skills, counted his pigs and cows, drew up a detailed family tree, and interviewed him about his "political reliability" and how closely he "guarded his Germanness."

Members of the elite SS had to get government permission to marry. An officer and his fiancee had to submit massive files documenting their heritage through six generations. The files show not only the painstaking work each applicant went through to trace families back to 1720, but also the efforts of faceless clerks who double-checked each entry in the thick folders.

Files of the Nazi Party's courts describe cases of party members charged with uttering defeatist slogans, listening to British radio or failing to reveal an acquaintanceship with a Jew.

A room filled with 10.7 million Nazi Party cards in their original cabinets also contains a file of people who were refused membership. Each rejection bears a reason: homosexuality, thievery, masturbation, or, in the case of a man who was refused in 1936, "treated by Jewish physician."

Over the years, the Germans have not seemed eager to get the documents back, even though the West German government has always paid for operation of the center as part of its obligation to support the postwar occupation.

But a West German government delegation went to Washington earlier this year and won the State Department's approval of a transfer, after the microfilming is completed.

Prosecutors and Jewish groups object to the restrictive German public records laws. While the U.S. Freedom of Information act gives virtually anyone the right to see files on dead people, German law permits only governments and scholars to see the files.

In addition, German privacy rights extend beyond death. That means that the file of Herbert von Karajan, the Austrian conductor of the Berlin Staatskapelle during the war, and later of the Berlin Philharmonic, would not be open to the public even now, a year after his death.

And that means the public would not be able to learn that von Karajan paid his initiation dues and applied to become a Nazi in 1933, although he always claimed that he joined the party much later and then only to be able to keep working as a musician.