Paris Together, they would make up a stunning gallery: 167 Renoirs, 166 Rembrandts, 175 Warhols and more than 200 works by Dali.
Experts have a tally of 170,000 pieces of missing art - many stolen from private homes, others taken from museum walls or pilfered from storerooms.
Only a small fraction are ever found: Interpol puts the figure at around 10 percent. Yet masterpieces like Edvard Munch's "The Scream" and "Madonna," recovered last week in Norway, turn up more often, partly because of intense police work and partly because they are so tough to sell.
Criminals sometimes mastermind a spectacular burglary, then discover nobody will touch a work of art so famous that any buyer would have to hide it from view, said Karl-Heinz Kind, a specialist officer on art theft at Interpol.
Thieves may demand a ransom, or try to sell works at a fraction of their worth. This is where some thieves trip up: The Italian house painter who stole the "Mona Lisa" in a famous 1911 heist was caught two years later when he tried to sell it.
After a robbery, "the second step is ... to make money out of it," Kind said in a telephone interview. "And that's the much more difficult part, and I think very often underestimated by the thief."
For lesser treasures, the market is lucrative, and vast.
The FBI estimates the market for stolen art at $6 billion annually. The Art Loss Register in Britain, which maintains the world's largest database on the subject, has tallied 170,000 pieces of stolen, missing and looted art, said staff member Antonia Kimbell.
Interpol has about 30,000 pieces of stolen art in its database. Most art thefts are ordinary burglaries of private homes, where criminals take everything of value they can find, including art, said Kind, the Interpol specialist. In museums, many thefts occur in storerooms, and sometimes go unnoticed for years until museums do inventory. Often, museum workers are involved, he said.
Then there are the dramatic raids. Kind wants to dispel the myth of art world criminals like Pierce Brosnan's suave character in the 1999 remake of "The Thomas Crown Affair."
"I would warn against considering art thieves as gentlemen thieves," Kind said. They are increasingly armed and violent, he said.
The Munch paintings were stolen by masked gunmen at the Munch Museum in Norway in 2004, while the museum was open. Police have said little about how they were recovered.
In February, gunmen raided the Chacara do Ceu Museum during Carnival celebrations in Rio de Janeiro. They made off with a Picasso, a Monet, a Matisse and a Dali before blending into the partying crowd.
One of the biggest art heists of all time took place in the United States. In 1990, two men disguised as Boston police officers walked into the Isabella Stewart Gardner Museum as the city's St. Patrick's Day celebration was winding down. They persuaded security guards to unlock the doors of the gallery and then stole 13 priceless items including works by Rembrandt, Vermeer, Degas and Manet.
That heist appears on the FBI's list of the top 10 art thefts. The list is topped by the looting of Iraqi artifacts following the U.S. invasion in 2003 - an event that galvanized the international community's response to cultural theft.
The following year, the FBI dedicated 12 agents to a special art crime team. During its first year in operation, the team recovered more than 100 pieces worth at least $50 million.