6 valuable works of art discovered in people's attics and garages

•Valuable works of art are not always displayed in museums or owned by private collectors or foundations. In some rare cases, they fell through the cracks - either because the artist didn't become famous until after his death, because the technology to properly verify the provenance of a work didn't exist, or because the owner wasn't savvy enough to give his realized they were sitting on - or staring at - a cultural gold mine.

Here are six cases where long-lost paintings have surfaced after years of being hidden in garages, attics or basements. Besides being amazed, maybe you'll gain the motivation to clean out your own storage spaces in search of forgotten treasures.

1. A CONTESTED CARAVAGGIO PAINTING

• Caravaggio, Judith Beheading Holofernes, late 16th to early 17th century Wikimedia Commons / Public Domain

~In 2014, French homeowners in Toulouse discovered much more than a puddle in their attic while trying to fix their leaky roof. Hidden in the rafters was a hidden painting that could be the handiwork of the Italian artist Caravaggio.

The painting - a version of the artist's Judith Beheading Holofernes (1599-1602), exhibited in the National Gallery of Ancient Art in Rome - was cleaned and analyzed in Paris, where experts debated its true origins. Some experts claim that Louis Finson - a 17th-century Flemish Baroque painter who studied and imitated Caravaggio's style - created the work, while others believe that the Renaissance master painted it himself earlier in the 1600. (According to Finson's will, the Flemish painter owned a copy of Judith Beheading Holofernes, but it disappeared about 400 years ago.)

Art expert Eric Turquin states that the Caravaggio attic is indeed authentic, citing its strokes, intricate details, and use of bright and energetic style as evidence. Other experts, such as British art critic Jonathan Jones, argue that the painting lacks the "psychological intensity" or signature realism of Caravaggio. Meanwhile, Caravaggio's contested work continues to be a magnet for controversy. In 2016, art historian Giovanni Agosti resigned from the board of Milan's Brera art gallery after the institution exhibited the work alongside authentic Caravaggio paintings.

2. A NEW AUTHENTICATED VAN GOGH LANDSCAPE

•In 1908, Norwegian industrialist Christian Nicolai Mustad acquired a 19th-century painting of the French countryside at sunset, called Sunset at Montmajour. It once belonged to Theo van Gogh, renowned art dealer and brother of Vincent van Gogh. Originally thought to be the famous artist's handiwork, the 1888 artwork was reportedly relegated to the attic after the French ambassador to Sweden visited Mustad's home and suggested it was a fake. It remained there until the collector's death in 1970.

-That said, you won't see the polarizing Judith Beheading Holofernes replica shown abroad anytime soon: the French government banned the canvas from being exported until November 2018 to prevent it from being seized by an international collector.

-The new owners suspected the painting might be a van Gogh, so they brought it to the Van Gogh Museum in Amsterdam in 1991. There, experts tentatively confirmed that the work was not authentic, in part because it lacked a signature. But a few years later, art historians used new technologies to re-examine the painting, leading them to a very different conclusion.

-In 2013, van Gogh historians announced that Sunset at Montmajour was indeed painted by the iconic post-impressionist painter. They noted that it was painted on the same type of canvas and using the same techniques as Van Gogh's paintings in Arles, France. It was also listed as part of Theo van Gogh's collection in 1890 and had "180"—the number of the painting in his collection inventory—painted on the back.

Adding to their certainty, an 1888 letter from Vincent to Theo described the painting in detail and even mentioned the very day he had painted it. (Before this, experts mistakenly believed van Gogh was referring to another painting, an 1888 work titled The Stones.)

~After confirming its authenticity, Sunset at Montmajoura was exhibited at the Van Gogh Museum in 2013. To date, it is the first large-scale painting by the Dutch artist to be newly authenticated since 1928.~