Photograph by Lewandowski/LeMage/Gattelet/Réunion des Musées Nationaux/Art Resource, N.Y.

Acquired through conquest, wealth, good taste, and plunder, those holdings were splendid and vast—so much so that the Louvre could lay claim to being the greatest repository of art in the world. With some 50 acres of gallery space, the collection was too immense for visitors to view in a day or even, some thought, in a lifetime. In the Salon Carré—the “square room”—alone could be seen two paintings by Leonardo da Vinci, three by Titian, two by Raphael, two by Correggio, one by Giorgione, three by Veronese, one by Tintoretto, and—representing non-Italians—one each by Rubens, Rembrandt, and Velázquez.

But even in that collection of masterpieces, one painting stood out from the rest. As the Louvre’s maintenance director, a man named Picquet, passed through the Salon Carré during his rounds on the morning of August 21, 1911, he pointed out Leonardo’s Mona Lisa, telling a co-worker that it was the most valuable object in the museum. “They say it is worth a million and a half,” Picquet remarked, glancing at his watch as he left the room. The time was 7:20 a.m.

Shortly after Picquet departed the Salon Carré, a door to a storage closet opened and at least one man—for it would never be proved whether the thief worked alone—emerged. He had been in there since the previous day—Sunday, the museum’s busiest. Just before closing time, the thief had slipped inside the little closet so that he could emerge in the morning without the need to identify himself to a guard at the entrance.

There were many such small rooms and hidden alcoves within the ancient building; museum officials later confessed that no one knew how many. This particular room was normally used for storing easels, canvases, and art supplies for students who were engaged in copying the works of the old masters. The only firm anti-forgery requirement the museum imposed was that the reproductions could not be the same size as the original.

Emerging from the closet in a white artist’s smock, the intruder might have been mistaken for one of these copyists—or, perhaps, for a member of the museum’s maintenance staff, who also wore such smocks, in a practice intended to demonstrate that they were superior to other workers. If anyone noticed the thief, he would likely be taken for another of the regular museum employees.

As he entered the Salon Carré, the thief headed straight for the Mona Lisa. Lifting down the painting and carrying it into an enclosed stairwell nearby was no easy job. The painting itself weighs approximately 18 pounds, since Leonardo painted it not on canvas but on three slabs of wood, a fairly common practice during the Renaissance. A few months earlier, the museum’s directors had taken steps to physically protect the Mona Lisa by reinforcing it with a massive wooden brace and placing it inside a glass-fronted box, adding 150 pounds to its weight. The decorative Renaissance frame brought the total to nearly 200 pounds. However, only four sturdy hooks held it there, no more securely than if it had been hung in the house of a bourgeois Parisian. Museum officials would later explain that the paintings were fastened to the wall in this way to make it easy for guards to remove them in case of fire.

Once safely out of sight behind the closed door of the stairwell, the thief quickly stripped the painting of all its protective “garments”—the brace, the glass case, and the frame. Since the *Mona Lisa’*s close-grained wood, an inch and a half thick, made it impossible to roll up, he slipped the work underneath his smock. Measuring approximately 30 by 21 inches, it was small enough to avoid detection.