The Mongol leader conquered more territory than any person in history, yet very little is known about what he looked like, how he died or even where he is buried. Legend has it that upon his death in 1227, the Great Khan’s soldiers honored his request to keep his gravesite a secret by butchering anyone who saw his funeral procession. They then ensured their own silence by killing themselves. Another account has the men concealing the grave by trampling it with 10,000 horses, and still another claims they diverted a river over it to protect it from robbery and desecration. Genghis Khan’s final resting place has since become one of the most sought after prizes in archaeology. Researchers suspect it may be located in Mongolia’s Khentii Province, but despite looking for it with everything from ground penetrating radar to satellite images, no team has yet to strike pay dirt.

The Austrian-born wunderkind first took up the harpsichord when he was just 3 years old. He composed his first piece of published music at age 5, and by his teen years, he had already written several concertos, sonatas, operas and symphonies. Mozart and his sister Maria Anna—herself a musical prodigy—traveled widely through Europe exhibiting their talents in royal courts and public concerts. From Bavaria to Paris, audiences marveled at the boy wonder’s ability to improvise and play the piano blindfolded or with one hand crossed over the other.

During a 1764 stopover in London, Mozart was even tested and examined by a British lawyer and naturalist named Daines Barrington, who was awestruck by the 8-year-old’s ability to sight-read unfamiliar music “in a most masterly manner.” Mozart would eventually grow into one of Europe’s most celebrated and prolific composers. Before his untimely death at age 35, he wrote more than 600 pieces of music.

Shortly after Augustus and his Roman legions invaded Egypt in 30 B.C., the enigmatic Queen of the Nile is said to have taken her own life by poisoning—possibly with a bite from an asp. Her suicide closely followed that of her paramour, Mark Antony, and the ancient chronicler Plutarch writes that the two star crossed lovers were then laid to rest “in splendid and regal fashion” in a tomb near Alexandria. The story trails off from there, however, leaving archeologists with a Sphinx-sized riddle. Some believe the mausoleum ended up at the bottom of the sea after fourth and eighth century earthquakes changed the topography of Alexandria, while others claim the couple may be buried near Taposiris Magna, an ancient temple that has yielded dozens of tombs and mummies.

In the late-1780s, a few years after he helped fuel the American Revolution with pamphlets such as “Common Sense,” the writer and political philosopher Thomas Paine finally found time to pursue his passion for scientific innovation. He experimented with a smokeless candle, early steam engines and a concentric wheel, and conducted an investigation into the causes of yellow fever. Still, he was most excited by the prospect of building iron bridges. “The European method of bridge architecture, by piers and arches, is not adapted to many of the rivers in America on account of the ice in the winter,” he argued in a 1786 letter to Benjamin Franklin. With this in mind, Paine drew up plans for a single arch iron bridge that employed a lattice support structure modeled after a spider’s web. He patented the design and tirelessly promoted it on both sides of the Atlantic, but proposed bridges over Philadelphia’s Schuylkill River, the Thames in London and the Seine in Paris all failed to materialize. The closest Paine came to getting one built was in 1797, when elements of one of his prototypes were incorporated into a bridge over England’s River Wear.

Born into a royal family of Huns, a nomadic people based in what is now Hungary, Attila rose to power alongside his brother, Bleda, in 434 A.D. A one-time ally of Rome against other barbarian groups, including the Burgundians and Goths, Attila accepted hefty subsidies in gold in exchange for not attacking Roman territory—then did it anyway. After having Bleda killed, he assumed total control of an empire that stretched across Central Europe. A complicated series of events involving Western Emperor Valentinian III and his sister, Honoria, inspired Attila to invade Gaul (present-day France) in 450. Though a combined force of Romans and Visigoths blocked the invasion, Attila was undaunted, and in 452 he invaded Italy. The Romans sent Pope Leo I as a peace emissary, and though the details of their meeting are unknown, Attila subsequently withdrew his troops and returned to Hungary. In 453, he was found dead the morning after his wedding (he had multiple wives), apparently the victim of a fatal nosebleed, accidental alcohol poisoning or a murderous conspiracy, possibly involving his new bride, Ildico.

Queen Elizabeth I’s favorite privateer met his end in Panama in 1596, having spent the previous two decades harassing Spanish holdings in the New World and undertaking a circumnavigation of the globe. After his death, Drake was dressed in his armor, sealed inside a lead coffin and given a traditional burial at sea some 14 miles off the coast of Portobelo. His remains have since been lost in the Caribbean, but that hasn’t stopped scores of divers, archaeologists and treasure hunters from seeking them out. A rare breakthrough came in 2011, when a mission financed by American entrepreneur Pat Croce found what is believed to be the wreck of two of Drake’s scuttled ships. The team also searched in vain for the navigator’s coffin, but the precise location of his 400-year-old watery grave remains a mystery.

Alexander died in Babylon in 323 B.C., having led his Macedonian armies on a decade-long campaign of conquest from Greece to India. In keeping with his famously immodest moniker, the deceased warrior-king was placed in a gold sarcophagus and coffin and eventually taken to a tomb in Alexandria. His body was moved to a mausoleum a few years later, where it became something of an ancient tourist attraction. Julius Caesar and Augustus both paid their respects, and Caligula supposedly looted Alexander’s armored breastplate during a visit in the 1st century A.D. The Roman Emperor Septimus Severus finally had the tomb sealed off for good sometime around the year 199. The trail goes cold from there, and some 150 search expeditions have failed to pick it up. Most researchers believe Alexander’s grave is still lurking somewhere in Alexandria, but others argue that it may have been moved to Venice, Greece or some other location in Egypt.