The theft that made the Mona Lisa the most famous painting in the world

She was famous before, but not like this. The Louvre’s own record is unusually direct about the turning point: the theft of the painting by Vincenzo Peruggia, a glazier working at the museum, in 1911 “gave it worldwide celebrity”, and it was only after its recovery in 1913 that La Joconde became “the principal masterpiece of the Louvre”.

A picture that had hung in French royal and national collections for nearly four centuries became the most famous painting on earth by being stolen off the wall by a workman.

What you are actually looking at

Lisa is seated in a pozzetto — a tub chair with a rounded back held by balusters — turned almost perpendicular to us, in front of a low balustrade with rectangular mouldings. At each end of that balustrade stands a small column, and between them opens a landscape of mountain chains and waterways: a winding road crossing the hills on the left, a bridge crossing the river on the right.

Now the correction, and it is the Louvre’s, not ours. It is endlessly repeated that the horizon on the left sits at a different height from the one on the right, and that this is what makes her expression unstable. The record says otherwise — the waterline runs continuously across the picture, partly concealed by the mountains. The asymmetry people describe is not there.

Her dress is not mourning either, though you will read that it is. The Louvre describes a rich, fashionable Florentine costume: a dress probably dark green, with detachable yellow sleeves, a white chemise showing at the shoulder slash, and a fine silk veil pinned at the chest with gold thread in a geometric interlace. Her hair is not loose — most of it is gathered in a bun under a bonnet you can barely see. Infrared reflectography is how we know that.

Why she looks different from her own reproductions

Because you are looking through roughly five centuries of other people’s varnish.

The Louvre is blunt about it: thick, uneven, oxidised varnish layers applied after Leonardo’s death, in later restoration campaigns, have yellowed into a filter over the whole surface. The effect is not subtle — it shifts the palette, turning the sky’s blue to green, and darkens the lower part of the composition.

Which is where the Prado’s version becomes extraordinary rather than a footnote. Madrid holds a copy painted in Leonardo’s own studio, alongside the original: the figures are identical in size and shape, transferred by tracing from the same cartoon, and every pentimento — every change of mind in Leonardo’s panel — is repeated in it. It was made at the same time, in the same room. Its landscape had been painted over in black; the Prado found it with infrared reflectography and raking light, confirmed it with X-ray, and uncovered it.

So the Prado panel is the nearest thing that exists to seeing the Mona Lisa’s colours unfiltered by four hundred years of varnish.

How it was made, and how fragile it is

Leonardo built her out of sfumato — thin oil glazes laid one over another until the transitions between tones become imperceptible and the contours dissolve. It is a technique of accumulation, not of drawing, and it is why the face refuses to resolve into edges.

He never finished. The Louvre points to the sketchy terrain at the lower right as unfinished ground, and the object history records that the painting was begun around 1503, probably for Francesco del Giocondo, but that Leonardo kept it until the end of his life, still working on it, still incomplete when he died.

The panel itself has had a hard time of it. The poplar has gone slightly convex with changes in humidity, and it split: an 11 cm crack runs down from the top edge, through the sitter’s hairline, and stops — the record says “almost miraculously” — at her forehead. On the reverse it was stabilised long ago with two butterfly joints and pieces of canvas. In 1956 a man threw a stone at her, breaking the protective glass and slightly damaging the left elbow.

One thing the panel has not suffered: it was never cut down. The bare edges and the ridge of paint at the border prove the picture is the size Leonardo made it.

Reading. The smile is the most written-about square inch in painting, and the Louvre’s own framing is careful: Leonardo’s aim was to show the sitter’s inner feeling without revealing its cause. The record also notes a possible pun — giocondo means “happy” in Italian, and she was Lisa del Giocondo. Whether the smile is a joke about her married name is a reading, not a record.

How she got to France

Not by conquest, and not by Napoleon. The record’s judgement is that the painting was “very probably acquired by François I in 1518” — Leonardo having brought it with him to France in 1516 and worked on it until his death. Vasari, writing in 1550, already places it with the French king at Fontainebleau, though he never saw it himself.

It entered the national collection with the Revolution: the acquisition field simply reads 1793, former royal collection, owner — the State.

Since then she has left the building three times in modern memory: to the United States in 1963, and to Japan and the USSR in 1974. She has not travelled since, and the record gives the reason plainly — extreme fragility.

What isn’t known

• Who she is — with certainty. The Louvre argues a solid 16th-century tradition identifies her as Lisa Gherardini (1479–1542), wife of the silk merchant Francesco del Giocondo, and supports it with a marginal note by Agostino Vespucci found at Heidelberg in 2005, dated October 1503. But the record also prints the awkward counter-evidence: Antonio de Beatis, who saw Leonardo’s studio in 1517, described a portrait of “a certain Florentine lady, painted from life at the request of the late Giuliano de’ Medici”. The Louvre works through the alternative candidates and rejects them — but it prints the contradiction rather than hiding it.
• When exactly François I acquired it. “Very probably” 1518, on the evidence of a payment to Salaì.
• The wood’s date. The record gives no dendrochronological results at all.
• Almost everything about the theft. One sentence: Peruggia, 1911, recovered 1913. The Louvre’s record does not narrate how it was taken, investigated or recovered — that story lives elsewhere.

Which leaves a pleasing shape. The most looked-at painting in the world is an unfinished portrait, on a cracked poplar board, seen through somebody else’s yellowing varnish, of a woman whose identity the museum defends rather than assumes — and it owes its fame to a man who walked out with it under his coat.

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