History Michelangelo's David at Risk From Weak Ankles Tiny fractures at the famous sculpture's ankles could prove devastating in the event of an earthquake. Continue reading →

Michelangelo's David risks crumbling down under its own weight because of the statue's weak ankles. Alarm bells sounded after researchers carried out a series of centrifuge tests on small-scale plaster replicas of the marble masterpiece. Apparently, damage caused by the statue's inclination is placing the great art work at risk, according to researchers at Italy's National Research Council (CNR) and the University of Florence. The experiments revealed that under high-stress conditions, the statue would break along small cracks currently visible in the left ankle and in the lower part of the carved tree stump supporting the right leg. Is This the First Self-portrait of Michelangelo? Such cracks are not unknown to experts. "They were first detected between 1852 and 1872 and nowadays they are more extensive than in 1872," Giacomo Corti, a researcher at CNR's Institute of Geosciences and Earth Resources, and colleagues wrote in the Journal of Cultural Heritage. Although they have been covered up with plaster over the years, the hairline cracks tend to reappear. They do not indicate an imminent collapse, but could prove devastating in the event of a major earthquake. The experiments consisted of several centrifuge runs. In the centrifuge, the 4-inch plaster replicas were affected by a force stronger than gravity, but otherwise playing the same role. Michelangelo's David Holding Secret Weapon? Positioned both vertically and inclined forward at angles of 5, 15 and 25 degrees, the models were subjected to increasing rotational speeds up to rupture. "In the vertical position, the gypsum model and, by analogy, the original masterpiece are in the most stable conditions, as indicated by rupture occurring at the highest acceleration well above the conditions of equilibrium," the researchers wrote. Video: Michelangelo's Face Revealed They noted that fractures typically occur in the lower portions of the legs. But as the statue's angle of inclination increases, the models break at lower rotational speeds, while cracks tend to develop progressively higher along the legs -- close to the right knee for inclinations between 15 and 25 degrees. "This means that the higher the inclination, the more unstable the statue becomes," the researchers said. The tests suggest the 5,572-kg marble statue would break under its own weight if standing at an inclination higher of 15 degrees. In such a scenario, the statue's pose and poor quality marble would contribute to the collapse. Michelangelo carved David from a single block of marble that two other sculptors, Agostino di Duccio and Antonio Rossellino, discarded as it had an imperfection. On Sept. 8, 1504, the towering sculpture, acclaimed for its depiction of male physical perfection, was displayed beside the main doorway of the Piazza della Signoria in Florence. 16th-Century Masterpiece Reveals Cheese Glue Recipe Representing the biblical hero who killed Goliath, the sculpture marked a watershed in Renaissance art and established Michelangelo as the foremost sculptor of his time at the age of 29. The statue remained in its original location, at the mercy of the elements, until 1873, when it was moved to its present location in the Galleria dell'Accademia. According to the researchers, the micro fractures currently visible on David are the result of a long-lasting, small forward inclination of about 5 degrees during the statue's time in Piazza della Signoria between 1504 and 1873. "The research confirms previous hypothesis and could help in the preservation of this masterpiece," Cristina Acidini, superintendent of Florence's museums, said. She reassured that the cracks do not pose an immediate threat. "Since 2001, David's micro fractures are constantly monitored and no variation has been recorded so far," Acidini told Florence's daily La Nazione. Image: from left to right: Michelangelo's David; details of the fracture system affecting the lower sections of the statue's legs; approximate location of fractures in the replica statue with angle of inclination between 0 and 5 degrees. Boxes with red contours shows the position of micro fractures in the original statue. Credit: CNR.

Oct. 18, 2012 -- This week, seven masterpieces, including paintings by Picasso, Matisse, Monet and Gauguin, were stolen in a pre-dawn heist at Rotterdam's Kunsthal museum. The heist was the biggest such theft in the Netherlands in two decades. One of the paintings stolen was the "Waterloo Bridge, London" by Claude Monet, shown here. Art museums have long had to contend with bold thieves who use cunning and sometimes sophisticated methods to pull off their crimes. Here’s a look at some other daring art heists.

More than one hundred years ago, Leonardo da Vinci's masterpiece, the Mona Lisa, became the world's most famous painting after it was stolen from the Louvre Museum in Paris on Aug. 21, 1911. Stolen by Vincenzo Peruggia, who claimed he fell in love with Mona Lisa after gazing into her eyes for the two years the painting resided in his kitchen. "La Joconde," as the painting is known to the French, was an international sensation -- as was the Louvre by virtue of association. The notoriety benefited the search for the painting, since it would have been impossible to sell to any collector able to pay. Peruggia, a laborer living in Paris, who once worked at the Louvre, simply removed the painting from the wall on a day that the museum was closed and walked out with the pilfered portrait hidden under his clothes. Although Peruggia cited Italian nationalism as the reason for stealing the painting, the prospect of the fortune he would gain from selling the Mona Lisa appears to be his true motive. Though, Italians have certainly not forgotten the painting's origins and have actively petitioned its return to Florence. This theft is among the best-known art heists in history.

To get an idea of the kinds of people who are behind these capers, take a look at Stéphane Breitwieser, who might have been the most successful art thief in history -- until he was caught. A waiter by trade, a self-taught art historian and traveler, Breitwieser stole 239 works of art from 1995 to 2001 worth an estimated $1.4 billion in total. He was caught in November 2001 while trying to pull off a heist from a museum in Lucerne, Switzerland. According to PBS, after Breitwieser was arrested, his mother burned over 60 of the stolen masterpieces. For his crimes, Breitwieser was sentenced to 26 months in prison. His mother served 18 months for being an accomplice.

On March 18, 1990, thieves disguised as police officers entered the Isabella Stewart Gardner Museum in Boston and pulled off what was the largest -- and still unsolved -- art heist in U.S. history. The thieves handcuffed the overnight guards of the museum under the false premise that there had been a warrant out for their arrest, according to the Boston Globe. Despite the fact that their movements were captured on video camera and by motion sensors, the criminals spent a total of 81 minutes conducting the heist. Johannes Vermeer's "The Concert" appears in this photo. With an estimated value of up to $200 million, this masterpiece is probably the most valuable artwork the criminals stole. (Continued on the next slide.)

Worth around $100 million, Rembrandt's "The Storm on the Sea of Galilee" was among the 13 masterpieces that the thieves stole in Boston. The total value of the artwork stolen in the heist has been pegged to just over $300 million, though some estimates put the number closer to half a billion dollars. The paintings were often cut from their frames, which leads investigators to believe that the perpetrators were not well-studied art thieves.

On Aug. 22, 2004, masked gunmen entered the Munch Museum in Oslo, Norway, and stole two Edvard Munch masterpieces, "The Scream" and "Madonna," in broad daylight, as reported by CBSNews. The pieces were recovered by police in 2006, though each work suffered slight damage, which required restoration before they went back on public display in 2008. "The Scream," the more famous of the two pieces and one of the most recognizable paintings in the world, is worth around $82 million, according to The Telegraph.

In February 2008 on a Sunday afternoon, armed men walked into the Foundation E. G. Bührle Collection in Zurich and stole four masterpieces worth an estimated $140 million, the largest art robbery in Swiss history, according to a report from The Telegraph. Paul Cézanne's "Boy in a Red Waistcoat," seen here, was among the paintings taken. The other three paintings include Claude Monet's "Poppies near Vétheuil," Edgar Degas' "Count Lepic and his Daughters," and finally Vincent Van Gogh's "Blossoming Chestnut Branch."

On May 21, 1988, thieves smashed a window on the ground floor of the Stedelijk Museum in Amsterdam, The Netherlands, and stole three paintings worth $52 million, according to the Associated Press. That figure would be closer to $100 million today factoring for inflation. Although the heist was the largest in Dutch history, the paintings were recovered two weeks later as the perpetrators attempted to sell their loot in a hotel transaction. "Sunflowers," by Van Gogh, a painting from the same series as one of the stolen artworks, appears in this photo.

"Luxembourg Garden" by Henri Matisse was among the paintings stolen by thieves from the Museu Chacara do Céu in Rio de Janeiro, Brazil. On Feb. 24, 2006, while the rest of the city reveled in the annual celebration of Carnival, four armed men escaped with this landscape as well works by Salvador Dali, Pablo Picasso, Claude Monet. The paintings have not yet been recovered and the value has not been estimated, according to the Federal Bureau of Investigation's Art Crimes Team.

Mona Lisa wasn't the only da Vinci painting famously absconded with by criminals. In August 2003, thieves disguised as tourists visiting Drumlanrig Castle in Scotland ran off in a white Volkswagon Golf with Leonardo's "Madonna of the Yarnwinder." The castle is home to an estimated $650 million worth of works by da Vinci, Rembrandt and Hans Holbein, according to the Daily Mail. Worth about $65 million, the 500-year-old painting was recovered. Prosecutors charged four men in connection with the crime.

On Dec. 22, 2000, Pierre-August Renoir’s "Young Parisian" and "Conversation with a Gardner" as well as a self portrait by Rembrandt disappeared from the National Museum in Stockholm, Sweden. Three men, one of whom threatened a guard with a submachine gun, escaped the museum with the three paintings in minutes. According to a BBC News report, police operated under the suspicion that others not at the scene of the robbery were assisting in its execution. As the armed theft was occurring at the museum, police were responding to call regarding car fires away from the scene of the museum just as the alarm sounded off. "Conversation with a Gardner" turned up during a drugs raid by police and the other two paintings were recovered in 2005. According to the FBI, the estimated value of the three items is around $30 million.