The term "barn find" rose to popularity and is often used to describe valuable cars that have been neglected in barns, gathering dust for decades. But the term can extend to mean any hidden treasure discovered in attics, cellars and closets. Collectibles with unbelievably high values can be stashed almost anywhere.

"The amazing thing [about barn finds] is they happen every day," said Curtis Dowling, art detective and host of the new CNBC Prime reality series "Treasure Detectives." "You'd imagine after all these years no one would have anything left."

So read on and take heed: If you don't use or sell off your valuables, your descendants will. And if you ever have to clean out a relative's house, always check the attic! Items that might not look like much can be pay dirt. One of the following discoveries turned out to be worth $70 million at auction.

By Colleen Kane
Posted 1 March 2013

Tune in to "Treasure Detectives" on CNBC Prime, Tuesdays at 9 p.m. ET

Last year, Karl Kissner stumbled onto a trove of century-old baseball cards that some people estimated could be worth millions of dollars. Kissner was going through items from his grandfather's attic in Defiance, Ohio, and found a box of 700 baseball cards in mint condition, which Carl Hench collected from candy packages when he owned a meat market. Joe Orlando, president of Professional Sports Authenticator, called an estimate of $3 million for the whole collection "conservative." A 37-card sampling of the collection sold for $566,132 with Heritage Auctions in August, and the rest will be sold over the next few years. Kissner calls the discovery a "blessing." The cards are being divided among members of his Hench family, most of whom plan to sell theirs.

A stash of 33 movie posters dating from 1930 and 1931 was found in an attic in Berwick, Pa., where they were possibly being used as insulation. They then sold at a country auction for $30,000. The posters were discovered stuck together in a stack with wallpaper paste, still in the chronological order in which they were posted at the cinema. With painstaking care, the posters were steamed apart to reveal the beautiful art and rich colors of classic Hollywood advertising, including titles such as "The Public Enemy" (one of just two known copies in existence), "Cimarron" and "Little Caesar." The collection brought in $503,000 at a March 2012 auction with Heritage Auctions. The individual poster that brought the most money was for the 1931 film "Dracula," one of just four copies, that brought $143,400.

In its younger and more beautiful days, this 1960 Aston Martin DB4 Series II Sports Saloon Mercedes was owned by Elvis, but in 1996 it was discovered in the "barn find condition" shown here. It remained like that for 14 years until it went to auction with Bonhams in December 2010 in Weybridge, England. Its estimated value was approximately $82,645, which was exceeded at auction when it sold for about $110,000.

An English brother and sister were cleaning out the family attic when they found a 16-inch vase dating to the reign of Emperor Qianlong (1735 to 1796). It sold at auction in 2010 for $69.5 million to an unnamed Chinese buyer—according to The New York Times, it was the highest price ever paid at auction for a Chinese antiquity. It was such a distinction for the suburban auction house, Bainbridges of Ruislip, that they incorporated the vase into their logo.

In 2011, Michael Rorrer was cleaning out his great aunt Ruby Wright's house in Martinsville, Va., after her death when he came upon a stash in the closet of 375 comic books. Now, thanks to Rorrer's deceased great uncle Billy Wright's expertly curated collection, which contained some of the highest-valued comics ever published, Rorrer and his family are about $3.5 million richer. Most of the comics range from 1938 to 1941 and include such titles even noncollectors know are worth fortunes, like Action Comics No. 1 or Batman No.1. Pictured here is Detective Comics No. 27 from 1939—the debut of The Batman!

February's auction of the estate of David F. Powers, who was the confidant and former special assistant to President John F. Kennedy, was called the Presidential Auction. As the site explains, numerous personal photos and effects of the late president and his family were discovered by Powers' family, locked away in a closet. The collection of more than 650 lots included photography, letters, documents and the only birthday card ever made for JFK from then-2-year-old son John John. The highest seller in the auction by McInnis was JFK's leather bomber jacket, which sold for $570,000.

This 1950 Ferrari 166 Mille Miglia was not really lost, but it was out of the public eye for nearly half a century (much like the car stashed in a barn in the 1981 song "Red Barchetta" by Rush). This rare intact example of the original Ferrari racing car (only 166 were made, per the name) went from disuse to the cover of the September/October 2006 issue of Cavallino Magazine and then was shown at the 2007 Cavallino Classic in Palm Beach, Fla.

A collection of Scottish and English bank notes was found in an Edinburgh house attic, including rare early bank notes from The Union Bank of Scotland, The Caledonian Banking Company and The Royal Bank of Scotland. The collection was valued at over $60,000.

"Treasure Detectives" takes you deep inside the world of arts, antiques and collectibles and asks the question: is it a fake or is it worth a fortune? Each week, the "Treasure Detectives" team meets collectors and verifies the authenticity of collectibles, artwork and antiquities using innovative technology and street smarts to determine whether they're sophisticated forgeries or extremely valuable collectors' items…answers that could cost or earn owners a small fortune.

"Treasure Detectives" airs Tuesdays 9 p.m. EST/PST