I wept, but about what precisely I cannot say. Much to my amazement, after having done everything possible to shut out the ubiquitous maudlin press coverage that engulfed the tenth anniversary of the 2001 terrorist attacks, I visited Michael Arad’s National September 11 Memorial in New York City—which was dedicated exactly a decade after the disaster—to find that it impressed me at once as a sobering, disturbing, heartbreaking, and overwhelming masterpiece. Arad’s inexorably powerful, enigmatically abstract pair of abyss-like pools, which demarcate the foundations of the lost Twin Towers, comes as a surprise to those of us who doubted that...