It's amazing how many items worth a lot of money are found in people's attics and lofts, from paintings by world-famous artists to stacks of gold, often because the owners simply have no idea of their worth. Read on to see some of the most incredible treasures that were discovered gathering dust. All dollar values in US dollars.

Last October, Henrietta Sitwell discovered a drawing wrapped in bubble wrap in the attic at Weston Hall, an English manor house. Part of the famous Sitwell family of writers and artists, Henrietta claimed she "instantly recognised [the drawing] as something special": a sketch by the Italian artist Giovanni Battista Tiepolo, an Old Master.

Tiepolo, whose works include the ceiling of the Santa Maria del Rosario church in Venice (pictured), was a prolific painter and printmaker. In 1936, the writer Osbert Sitwell bought a Tiepolo sketch of traditional Italian clowns known as Punchinelli, but for 85 years it remained hidden in the attic. Dreweatts Auctioneers gave it a "conservative" estimate of £150,000-£250,000 ($204k-$340k). However, the closing bid when the Tiepolo sketch went up for auction in November 2021 was £100,000 ($131.5k).

A Frenchman inherited a property in Normandy from a relative. When he moved into the house in 2016, much to his surprise he discovered a huge collection of old coins and bars of gold hidden within the house.

The hefty treasure, which weighed more than 220lb (100kg) in total, was valued at around $3.5 million (£2.6m). After inflation, that's over $4 million (£3m).

In 2015, an oil painting that had been sitting in an owner's loft for eight years was initially valued by auctioneer Richard Bromell at just $395 (£300). However, the tiny nine inches by seven inches painting was discovered to be painted by a 'follower' of 16th-century Renaissance artist El Greco.

It went on to be sold for an incredible $157,370, the equivalent of almost $190,000 (£145k) today. Unsurprisingly, the owner was thrilled to learn how much it sold for. Auctioneer Mr Bromell, who works at the Charterhouse auction house in Dorset, England, said: "It was a very interesting picture and very hard to value."

When homeowners in Toulouse decided they needed to mend their leaky roof in 2014, little did they know that they would find a 400-year-old painting, believed by some scholars to be by the Italian master Caravaggio.

Experts in the art history world heralded it as one of the most important paintings to emerge in modern times. The painting has caused much controversy in France however, with some scholars doubting whether it is a genuine Caravaggio at all. Despite this, France put an export ban on the painting to keep it in the country, with specialists estimating that the piece could fetch €120 million at auction. That's around $158 million (£121m) today. Shortly before the auction took place, however, it was bought privately by the hedge fund manager J. Tomilson Hill for an undisclosed sum.

In 2013, the owners of a Vincent Van Gogh painting that once belonged to the late Norwegian industrialist Christian Nicolai Mustad got the shock of their lives. They'd bought the landscape from Mustad's estate in 1970. Before that, the artwork had spent over 60 years in Mustad's attic, where he'd banished it after a supposed expert told him the painting was a fake. Despite having the painting examined several times, it wasn't until 2013 that specialists discovered the work was genuine and came from the same era of Van Gogh's career as Sunflowers, The Yellow House and The Bedroom. 

Known as Sunset at Montmajour, the painting has been likened to Sunflowers in both size and quality. An original Sunflowers sold at auction for $39.9 million (£30.2m) in 1987 – the equivalent of $99.6 million (£76m) in today's money – and it's likely this artwork is worth a similar amount. However, there are no records that the original owners have ever sold the painting.

When Michael Rorrer's great aunt died in 2012, he was tasked with cleaning out her Virginia home and deciding what to keep and what to throw out. Fortunately, he had his eyes peeled and discovered an old comic book collection. He didn't immediately think the comics were anything special though and merely put them in a box to take home.

It was only when he started flicking through them that he noticed the collection contained some vintage comics that might be of value. The golden-age comic books eventually sold for a staggering $3.5 million ($4.3m/£3.3m today) and included a copy of the original Batman comic from 1940.

The 19th-century artist Henry Arthur McArdle is most famous for painting The Battle of San Jacinto, an artwork that depicts a pivotal battle from the Texas Revolution in 1836 and is hung in the Texas State Capitol. McArdle reportedly painted a small version of the same artwork in 1901, but for almost 100 years the canvas was nowhere to be found. 

That changed in 2010 when one of McArdle's descendants, Jon Buell, stumbled across the painting in his grandmother's attic. Hidden beneath a tarp and "very, very dirty", the artwork had apparently been stashed away since the 1930s but Buell's grandmother believed the "working drawing" was worthless. The second Battle of San Jacinto was authenticated by experts and sold at auction for $334,000 (£255k) to an anonymous buyer in Texas. Adjusted for inflation, that means the painting is worth around $435,000 (£332k) today. 

A couple from Dumfries in Scotland bought this glass vase for the bargain price of $1.45 (£1) at a local car boot sale. The pair revealed they only bought the vase because they liked the plant it was holding. When the plant died, the vase was put in the loft and forgotten about.

It was only in 2008 when the BBC's Antiques Roadshow TV show came to town that the couple sifted through old junk in their house and decided it might be worth bringing along the vase that they had bought for next to nothing.

The vase turned out to be a highly desirable piece by world famous Art Nouveau icon René Lalique. In fact, it was the most valuable piece of glass to have appeared on the popular TV show and later sold for $46,000 (£32.5k). That's over $60,000 (£45.8k) today.

When Thomas Schultz and Lawrence Joseph bought a cottage in Long Island, New York in 2007, they discovered a massive collection of paintings in the attic.

The collection was made by a little-known artist named Arthur Pinajian, who used to live in the house. Like many artists, he found neither fame nor fortune in his lifetime and actually instructed that his art be thrown away when he died. His lost art is now much sought-after and the pictures found in the attic were valued at an incredible $30 million, the equivalent of $41 million (£31m) in 2022. 

Now take a look at some valuable treasures people couldn't keep