In the 21st century, we tend to look back at ancient technologies with an air of superiority. But there are more than a few inventions and artifacts that reach beyond modern understanding. Some may be nothing more than legends, but if you could recreate any one of these objects, you would easily change the world.

Stradivarius Violins

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Antonio Stradivari lived from 1644 to 1737. He was an Italian luthier and craftsman who we know as the most significant and greatest artisan in instrument-making history. Today, somewhere around 500 of his violins survive and sell for tens of millions of dollars.

The exact techniques and materials used to make violins and other instruments were passed down to Stradivari's eight heirs, but today the technique is lost. Researchers can only make their best estimates about the craftsmanship. One theory is that the wood the violins are made of grew during the small ice age, and was extra dense and unique.

Greek Fire

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Naval warfare in ancient Byzantium was pretty terrifying, especially to the eyes of the western European crusaders who saw the Byzantines incinerate naval ships even as they floated on the water.

Greek fire was used from the 7th to the 12th century AD and was even more powerful than simply igniting a flammable ship. The blast was accompanied by "thunder" and smoke, and the resulting fire could not be extinguished with anything except sand, vinegar, or large quantities of urine. Was this an ancient form of gunpowder?

Warriors even carried Greek fire grenades that they launched by hand or using small catapults. The exact composition of this ancient Greek compound was a state secret and is unknown even today.

Damascus Steel

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Damascus steel is represented in "Game of Thrones" as Valerian Steel. Both materials are stronger and more resilient than normal blades. Legends once told of Damascus steel being able to split a hair, easily slice other swords in half, and cut through rifle barrels.

The real Damascus steel swords have a pattern of banding on them that looks like flowing water. They are named after Syria's capital city, one of the oldest inhabited cities in the world, but no one actually knows if the steel was forged there.

In the 1700s, the knowledge of how to make Damascus steel was lost.

Flexible Glass

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Humans have been using naturally formed glass, like obsidian, since the stone age. The earliest known glass objects were dated back to the third millennium BC, and this beautiful Roman glass cup is from the 4th century AD.

A Roman legend says that there was once such a thing as flexible glass.

Pliny the Younger, Petronius, and Cassius Dio all told the story of a brilliant glass worker or alchemist who created something so amazing that it was brought to the court of Emperor Tiberius Caesar between 14–37 AD.

Isidore of Seville wrote that the emperor took the bowl of flexible glass and threw it to the floor. The bowl was dented but did not break. The craftsman fixed the dent with a small hammer and proclaimed that only he knew how to make flexible glass. Tiberius, afraid that the new material could undermine the value of gold and silver, had the man beheaded.

Mithridatum

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A cure-all elixir sounds like something out of a video game. But this 65-ingredient potion was said to be the antidote to any poison. The exact recipe is unknown and has changed through the ages. It was invented by Mithradates VI, King of Pontus, who thought that his mother was poisoning him in small doses.

The story goes that the king even tried to kill himself, but no poison would work. The recipe for Mithridatum was found in his cabinet and taken to Rome by Pompey. In Rome, it was made by Nero's physician Andromachus and Marcus Aurelius's physician Galen.

In the Middle Ages and up until 1786, Mithridate was taken to prevent the plague and as a cure-all. Oliver Cromwell even found it cured acne.

Roman Concrete

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Many Roman aqueducts, roads, and temples are still in surprisingly good condition. Even their ancient harbors are doing well after 2,000 years of being pummeled by the sea.

Roman concrete is as old as the Ancient Romans themselves. It is the most durable type of cement, and its recipe includes volcanic ash, which prevents cracks in the material. It made creations like the Pantheon, the world's largest unreinforced concrete dome, possible.

Unlike Roman cement, today's cement wears out in seawater after only half a century, and its production uses more energy and even creates greenhouse gases. If Roman cement could be reproduced today, it would completely replace modern cement.

The Cold Fusion Conspiracy Theory

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Eugene Mallove was a professor, scientist, and publisher of Infinite Energy magazine. He was a notable supporter of cold fusion research.

Cold fusion is a type of energy generated when hydrogen interacts with various metals. No radioactive materials are used in cold fusion, so there is no danger of radiation and no radioactive waste.

One of Mallove's books details a 1989 experiment into cold fusion at the University of Utah. He claims that there was energy output in several trials and that the findings were suppressed by mainstream physicists who called cold fusion "fringe science."

While he was cleaning out his childhood home in 2004, Mallove was murdered by the son of a former renter of the property. Three people were arrested and charged in connection with the slaying. No one has been able to document cold fusion after Mallove.

Tesla's Death Ray

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Tesla claimed to have worked on a directed-energy weapon for about 40 years. In 1937, he said "It is not an experiment... I have built, demonstrated and used it. Only a little time will pass before I can give it to the world."

Around this time, Tesla built something like a laser or particle beam accelerator. He brought his invention to the attention of the U.S. Army, saying that it could reach incredible distances and potentially bring down aircraft—a brand new kind of weapon.

Tesla himself noted that "death ray" was a misnomer since the device was a particle projector. Supposedly, no one took him up on backing that particular invention.

Starlite

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In the 1970s, amateur chemist Maurice Ward was busy creating his own hair products. Instead, he accidentally made a heat-resistant material called Starlite.

In 1993, Starlite was featured on the BBC technology show "Tomorrow's World." On the show, an egg was covered with Starlite and a blowtorch was set to it for ten minutes. The egg was cracked open and still raw. Theoretically, Starlite could protect the human body from the heat of a nuclear explosion.

Ward was extremely protective of his invention, so it never became mainstream. Ward died in 2011, having never partnered with any firm to bring the product to market. Some say Starlite was sabotaged or bought by the government.

Despite interest from NASA and other major technological companies, Ward never revealed the composition of Starlite, which is still unknown. Ward once mentioned that his close family knows the fabrication process, but after his death neither his wife nor any of his four daughters have produced any sample to demonstrate that they know the process.

Archimedes's Fire

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Archimedes of Syracuse was born in 287 BC and was one of the most brilliant mathematicians in history.

He was the mastermind behind this game-changing weapon. Using angled mirrors, he could combust the ships of any enemy who dared attack Syracuse. In seconds, the vessels would be fully engulfed in flames.

The Mythbusters tried to recreate this invention but had trouble directing the light from their mirrors onto a point small enough to ignite the boat. However, in 2005, a group of MIT students almost fully recreated the "burning glass" fires.