Armed with power tools, a crane lift, motorbikes and a plan straight out of a movie, four thieves broke into the Louvre Museum to steal jewellery once worn by France's queens and emperors.
It happened in broad daylight, while the museum was open, and took just 4 minutes.
With the thieves still at large and an investigation underway, attention has now turned to what will happen to the jewels.
Here is what experts say the thieves could be considering and why they were stolen in the first place.
Why were the jewels stolen?
We don't know.
The only way we'll find out the truth is if the thieves are caught.
But associate professor in art history at the University of Sydney Donna Brett said there could be a number of different reasons.
"It could be a targeted theft for someone who wants the jewellery," Dr Brett said.
"In these types of scenarios, the stolen material could also be used as collateral for drug deals and other sorts of international reasons."
Margo van Felius, a lecturer of international organised crime at Griffith University, said it was likely the jewellery was stolen for an underground private collector.
"They could have been stolen on demand or on order, and it may have been that only one piece was targeted but they grabbed some others as well," Dr van Felius said.
What jewels were stolen from the Louvre?
A total of nine objects were targeted, but only eight were actually stolen.
The crown of Empress Eugénie was found outside the museum.
The thieves apparently dropped the piece, made of gold, emerald and diamonds, as they made their getaway.
All are from the 19th century and once belonged to French royalty or imperial rulers.
France's Ministry of Culture said the stolen items were:
- Tiara from the jewellery set of Queen Marie-Amélie and Queen Hortense
- Necklace from the sapphire jewellery set of Queen Marie-Amélie and Queen Hortense
- Earring, part of a pair from the sapphire jewellery set of Queen Marie-Amélie and Queen Hortense
- Emerald necklace from the Marie-Louise set
- Pair of emerald earrings from the Marie-Louise set
- Brooch known as the reliquary brooch
- Tiara of Empress Eugénie
- Large bodice knot (brooch) of Empress Eugénie
What will happen to the jewels?
There's a bit of disagreement amongst experts about what the thieves will do with the jewels.
Some believe they will attempt to break the jewels and sell the pieces separately to avoid detection.
Arthur Brand, an art detective from the Netherlands, told ABC NewsRadio it was unlikely the jewels would ever be recovered.
"If there's some gold and silver, they can melt it down so it's really a race against time," Mr Brand said.
"If the police catch these guys within a week, the loot might still be there but if it takes longer, they might have dismantled these objects and sold the diamonds separately by then."
Tobias Kormind, managing director of 77 Diamonds, also said recovery would prove difficult.
"It's unlikely these jewels will ever be seen again," Mr Kormind said.
"Professional crews often break down and re-cut large, recognisable stones to evade detection, effectively erasing their provenance."
Most experts are in agreement that it would be "pretty silly" to sell the precious items as they are, given they are too well-known worldwide.
That is why Alexandre Giquello, the president of Drouot auction house, said that even disassembling the jewellery posed a high risk for potential buyers and the thieves themselves.
"Ideally, the perpetrators would realise the gravity of their crime and the dimension they've entered into, and return the items, since the jewels are completely unsellable," Mr Giquello said.
"Even beyond selling the items themselves, if they were to dismantle them — separating the precious metals, gemstones, pearls — everyone involved in the chain of responsibility, including those who recut the pieces and attempt to sell them, would be exposed to very serious penalties."
Experts have likened the crime to the 1911 theft of the Mona Lisa, noting that the thief at the time did not realise the scale of his act and the painting ended up under his bed.
French President Emmanuel Macron vowed in a social media post that the stolen jewellery would be recovered.
Will breaking down the jewels decrease their value?
Yes.
Dr van Felius said that would decrease their value.
"The value in the jewels is also in the history behind the stones and if you break them up and can't provide their provenance, then they do lose significant value," she said.
"If you decide to break the jewels, there is also a risk that you'll damage them in the process."
Ms Brett said all stolen goods lost value.
"Scotland Yard estimates most stolen goods are lucky to be sold at 10 per cent of their true value."
How much are the jewels worth?
We don't have a figure on that.
Officials have described the haul as of "inestimable" historical value.
French Interior Minister Laurent Nuñez emphasised that the stolen items represented French heritage and held universal significance, making their value impossible to measure in monetary terms.
What we do know, though, is that the thieves did not target or steal the world-famous Regent Diamond, which is housed in the same gallery.
Sotheby's estimates the Regent is worth over $US60 million ($92 million).
