© Getty Images

The Amber Room -

The Amber Room was constructed in the Catherine Palace in the 18th century, near St. Petersburg, Russia. The room contained gold-gilded mosaics, mirrors, and carvings, along with panels constructed out of about 1,000 pounds (450 kg) of amber. During the Nazi invasion in 1941, the room's panels and artwork were disassembled and taken to Germany. They haven't been seen since. A reconstruction of the room was built in 2003.

© Getty Images

Florentine Diamond -

The yellow 137-carat Florentine Diamond was likely from India and made its way to Europe by the end of the 15th century. However, how and exactly when it got to Europe is a matter of debate. After the fall of the Austrian Empire after World War I, the stone was taken into exile with Emperor Charles I of Austria. The stone was then stolen some time after 1918, and possibly cut into smaller diamonds.

© Getty Images

Sappho's lost poems -

The Greek lyric poet Sappho, who lived in the 7th century BCE, was highly regarded by the ancient Greeks. Considered to be one of the best poets of her time, sadly, few of her poems survived.

© Getty Images

Lost imperial Fabergé eggs -

Between 1885 and 1916, the Russian jewelry company House of Fabergé made ornately decorated Easter eggs for the Russian imperial family. The Russian Revolution in 1917 led to the execution of the Romanov family the following year. In the aftermath of their deaths, some of the eggs went missing and are still unaccounted for today.

© Getty Images

Menorah from the Second Temple -

The Menorah from the Second Temple in Jerusalem was looted by the Romans in 70 CE, and put on display in the Temple of Peace in Rome. The temple burned down in 191 CE, and the Menorah's fate has been uncertain since. Pictured is the Menorah depicted on the Arch of Titus in Rome.

© Getty Images

Peking Man -

In 1923, the fossils of a hominid, known as the Peking Man, were discovered in a cave near the village of Zhoukoudian in China. But the fossils disappeared in 1941, during the Japanese invasion of China, and their location today is still unknown.

© Getty Images

Yamashita's gold -

Yamashita's gold is alleged war loot stolen by the Imperial Japanese Army from Southeast Asia and hidden in the Philippines. Though there are accounts that claim the treasure remains hidden in the Philippines, its existence has been dismissed by most experts. It was named after the Japanese general Tomoyuki Yamashita.

© Getty Images

The lost painting of Raphael -

During the early 16th century, Italian painter Raphael painted the striking 'Portrait of a Young Man,' which is widely believed to be a self-portrait. The painting was owned by the Czartoryski Museum in Krakow, Poland, but during World War II Nazi officials stole it. Many historians regard it as the most important painting missing since WWII.

© Public Domain

Jules Rimet trophy -

The Jules Rimet Cup was the original trophy of the FIFA World Cup from 1930 to 1970. In 1970, Brazil won the competition for the third time, and, according to FIFA rules, the first team to win three times would gain permanent possession of the trophy. It was therefore sent to Brazil. In 1983, it was stolen in Rio de Janeiro and hasn't been seen since.

© Getty Images

Royal Casket -

In 1800, Poland's Princess Izabela Czartoryska created the Royal Casket, which contained 73 precious relics from the royal families who had ruled the country. Looted by Nazi officials during WWII, the casket's contents are now lost.

© Public Domain

Scepter of Dagobert -

Originally part of the French Crown Jewels, it's considered to have been its oldest part, dating back to the 7th century. Stored in the treasury of the Basilica of Saint-Denis in Paris until 1795, it hasn't been seen since then.

© Getty Images

The Tsar's Treasure -

In 1909, US$3 million in newly minted coins sent to the Russian Baltic Fleet, and an $800,000 government shipment in mixed coins to the American Atlantic Fleet, were lost when the RMS Republic sank off the coast of New England after a collision.

© Public Domain

'Love's Labour's Won' -

'Love's Labour's Won' is a lost play by William Shakespeare. Written before 1598 and published by 1603, no copies exist today. However, some scholars believe that records of 'Love Labour's Won' refer to another play by Shakespeare: 'Much Ado About Nothing.'

© Getty Images

Patiala Necklace -

Made by Cartier in 1928 for Bhupinder Singh of Patiala, then Maharaja of Patiala, the necklace had five chains and contained 2,930 diamonds. It vanished from the Royal Treasury of Patiala around 1948. However, some diamonds were later recovered.

© Public Domain

Sword of Islam -

The Sword of Islam was a ceremonial weapon given in 1937 to Benito Mussolini from Berber collaborators in Italian Libya. It disappeared in 1943, after Mussolini's summer residence was destroyed by the Italian Resistance.

© Getty Images

Romanian Treasure -

The Romanian Treasure is a collection of valuable objects and the gold reserves of the Romanian government, sent to Russia for safekeeping during WWI. But these were confiscated after the October Revolution and only some of the objects, and none of the gold reserves, have been returned.

© Public Domain

The Three Brothers -

The Three Brothers was a piece of jewelry created in the late 14th century, which consisted of three rectangular red spinels arranged around a central diamond. Owned by key historical figures such as Duke John the Fearless of Burgundy, the German banker Jakob Fugger, and several English monarchs, it vanished from records after 1645.

© Public Domain

Michelangelo's 'Leda and the Swan' -

Produced in 1530, this painting by Michelangelo depicts a scene from ancient mythology where the god Jupiter, taking on the appearance of a swan, seduces Leda, the queen of Sparta. Now lost, many believe it was destroyed due to its then controversial and erotic nature.

© Getty Images

Michelangelo's 'Head of a Faun' -

'Head of a Faun' is a lost sculpture by Italian Renaissance master Michelangelo, dating from 1489. The Bargello Museum in Florence, Italy, owned the sculpture, but it was stolen by German soldiers in 1944 from Castello di Poppi, a castle in Tuscany. It hasn't been seen since.

© Getty Images

Irish Crown Jewels -

The Irish Crown Jewels were a jewelled badge and star created in 1831 for the Grand Master of the Order of St Patrick, an order of knighthood established in 1783 by George III. Stolen in 1907 from Dublin Castle, the theft has never been solved.

© Public Domain

Nelson's Chelengk -

A chelengk was a military decoration of the Ottoman Empire. A special one made with diamonds was given to Admiral Horatio Nelson for his naval service in the Battle of the Nile. Placed in the National Maritime Museum in London in 1929, it was stolen in 1951. Nelson is seen here wearing it on his hat.

© Public Domain

Ark of the Covenant -

According to the Hebrew Bible, the Ark of the Covenant was a chest that held tablets engraved with the Ten Commandments. Once kept in Jerusalem, it disappeared during the Babylonian invasion of 586 BCE. It's unclear what happened to it or its whereabouts.

© Getty Images

Carvaggio's 'Nativity with St. Francis and St. Lawrence' -

The 'Nativity with St. Francis and St. Lawrence' was created in 1609 by Italian painter Caravaggio, depicting the birth of Jesus. It has been missing since 1969, when it was stolen from the Oratory of Saint Lawrence in Palermo, Italy. It's long been suspected that members of the Sicilian Mafia carried out the heist.

© Getty Images

The Llanganatis treasure -

The Llanganatis treasure is a lost Inca treasure of gold and other precious items supposedly hidden deep within the Llanganates mountain in modern-day Ecuador. Originally intended as part of the ransom of Inca emperor Atahualpa, it would have been hidden once it became known that conquistador Francisco Pizarro's men had killed the emperor.

© Getty Images

Twin Sisters -

The Twin Sisters were a pair of cannons used by Texas Military Forces during the Texas Revolution between 1835 and 1836. Their disappearance and ensuing search efforts have colloquially dubbed them the "Texas Holy Grail."

© Shutterstock

The Just Judges -

The Just Judges panel was part of the Ghent Altarpiece, a 15th-century work of art painted by Hubert and Jan van Eyck in Saint Bavo's Cathedral in Ghent, Belgium. The panel was stolen in 1934, and has never been found.

© Public Domain

Treasure of Lima -

A buried treasure filled with gold, silver, and jewelry, it was removed as a preventative measure in 1820 by the Peruvians fighting for independence from the Spanish. Believed to be buried on Cocos Island in Costa Rica, it's estimated to be worth up to US$208 million in today's money. However, the Treasure of Lima has never been recovered.

© Getty Images

Honjō Masamune -

The Honjō Masamune was a samurai sword, created by the master sword maker Gorō Masamune between 1288 and 1328 CE. The sword was passed down over the centuries from shōgun to shōgun (military dictators), but was lost during the US occupation of Japan in 1945.

© Getty Images

The original British Crown Jewels -

King John infamously lost the Crown Jewels while trying to cross The Wash estuary in 1216. Scientists believe that the monarch's treasure was seized by the sea as a result of a large and powerful tide.

Sources: (Live Science) (The Collector) 

See also: Proposed US states and territories that never were

© Getty Images