The Flor de Mar was a Portuguese ship that participated in numerous Indian Ocean conquests. It was returning home in 1511 after the conquest of Malacca when it sunk with over $2 billion worth of valuables in today’s money. The wreck has never been found.

The 137 carat Florentine Diamond was last owned by the infamous Medici family. Knowledge of its whereabouts ended with the family’s lineage in 1737.

1925’s Cartier Patiala Necklace features five platinum chains and 2,930 diamonds, including the 234.65 carat yellow “De Beers Diamond.” Seen here as worn by Maharaja Yadavindra Singh of Patiala, the necklace "disappeared" from the Royal Treasury in 1948. In 1998, part of the necklace was found at a second-hand jewellery shop in London by Eric Nussbaum, a Cartier associate. Predictably, the jewels were missing, however the De Beers Diamond also reappeared and sold at auction for $3.16 million in 1982.

Originally considered an “Eighth Wonder of the World," the Amber Room was a chamber in the Catherine Palace of Tsarskoye Selo near Saint Petersburg. The room was originally looted by the Germans in 1944, and dismantled for safekeeping when Allied forces closed on the position. It is unknown where the room was stored, or whether it survived bombing.

Portrait of a Young Man by Raphael went missing at the end of WWII. All signs point to it having been sold for traveling money by German Hans Frank.

The tombs of Alexander the Great, Cleopatra and Marc Antony have never been found. They are all most likely buried beneath the modern city of Alexandria.

The 1990 Isabella Stewart Gardner Museum theft might be the most famous art heist in history, and despite significant official and independent detective work, the 13 paintings have never been found. The collection, including multiple Rembrandts, is likely in a basement somewhere.

As many as 69 Faberge Eggs were created in Russia in the late 1800s, with 57 still around today. There are about seven missing, and only a black and white photo, and descriptions remain as proof of their existence.

The Three Brothers is a piece of jewelry worn by many British royals that featured three large rubies surrounding a central diamond, as well as pearls. King Charles I sold it for money in 1645, and it was never seen again.

Aztec emperor Montezuma II was murdered by Hernan Cortes and his Spanish conquistadores in 1520, and Cortes tried to get away with stealing a significant portion of Tenochtitlan’s gold. However, Aztec forces caught up to, and took revenge on Cortes. That gold is likely scattered around the outskirts of modern day Mexico city.

The Heirloom Seal of the Realm, also known as the Imperial Seal of China, was created in 221 BC by the Qin dynasty. At some point, the heirloom was lost during the Five Dynasties and Ten Kingdoms period from 907–960. The artifact is priceless, and practically worth billions.

Amaro Pargo was a Spanish “gentleman” pirate in the early 1700s. Although most of his spoils were passed down to his heirs, his personal treasure chest was never found. Supposedly its contents and location are recorded in a book marked by the letter “D,” but that book has also never been found.

The enormous golden menorah from the 2nd temple. The Romans took it after sacking Jerusalem. Some people think it’s being hidden by the Vatican, but others believe it was melted down and will never be found.