The Mona Lisa disappeared from the Louvre on 21 August 1911. The museum describes its recovery in Italy more than two years later, when an attempted sale alerted the authorities. The theft spread the painting’s fame far beyond the gallery in which it had hung.
That change in public recognition puts it above Paris’s modern-art losses. Gardner wins because prolonged absence across many works outweighs fame in our criteria. Put worldwide notoriety first and this could be #1: the best-known case is not automatically the deepest continuing loss.
Source: Louvre.
Image: Leonardo da Vinci · Public domain. Resized and recompressed; original rights retained.
