January 27, 1945—the date of the liberation of Auschwitz—is commemorated in Germany as Holocaust Day, and this year it was marked by vandalism. The Holocaust Memorial in Berlin was defaced, evidently by neo-Nazis, who treated it as if it were a public latrine. Even more distressing is the revelation that such vandalism has been a constant problem since the memorial’s opening, a problem that has been deliberately downplayed by city authorities, allegedly to discourage copycat acts.

Since the controversial memorial’s site was selected in 1992, fear that it would invite just this sort of vandalism has abounded. It stands at the very epicenter of Berlin, just south of the Brandenburg Gate, around the corner from the new American embassy. But now we see that it is not the location of the memorial but its peculiar design that makes it prone to defacement. Designed by Peter Eisenman, the monument consists of some 2,711 concrete pillars, or stelae, arranged on a rigid geometric grid and spreading out over five acres. The paths between these pillars are so narrow that only one person can comfortably pass between them. Eisenman’s intent, it seems, was to make the viewer’s confrontation with the monument’s bleak, pitiless geometry as intense and solitary an experience as possible. Too solitary, alas: it clearly offers an endless number of secluded corners for mischief.

When the memorial opened two years ago, Eisenman resisted attempts to make it more secure against vandalism, including restrictions on admittance and on behavior within the memorial. He stalwartly argued for the right of children to play on the site, and to jump from pillar to pillar, saying that these activities evoke “the sounds of life” of an urban Jewish neighborhood. A memorable battle he lost in this arena was his objection to the treatment of the concrete pillars with an anti-graffiti coating. Eisenman told reporters that graffiti ranks as a healthy and legitimate creative outlet in his native New York, and that he “didn’t want the graffiti coating” because he considers vandalism “an expression of the city.”

Any thriving city, we should recognize, can express many things. The trick lies in recognizing which of these expressions constitutes a death threat—an obligation all the more incumbent on the Berlin authorities for the tragic gravity of the monument’s origin and purpose.