<p>Although many of life's great mysteries remain unsolved, there are some lesser known ones that also have stumped researchers for centuries. Here's a look at some of the most intriguing historical mysteries, from the mysterious, and blonde, Tarim mummies from China to the undecipherable Voynich manuscript to lost city of Helike.</p>
Disappearance of the Indus Valley Civilization
<p>With a culture that stretched from western India to Afghanistan and a population numbering over 5 million, the ancient Indus Valley people — India's oldest known civilization — were an impressive and apparently sanitary Bronze-age bunch. The scale of their baffling and abrupt collapse rivals that of the great <a href="http://www.livescience.com/history/060105_maya_writing.html">Mayan</a> decline.</p> <p>But it wasn't until 1922 that excavations revealed a hygienically-advanced culture that maintained a sophisticated sewage drainage system and immaculate bathrooms. Strangely, there is no archaeological evidence of armies, slaves, social conflicts or other vices prevalent in ancient societies. Even to the very end, it seems, they kept it clean.</p>
The Tarim Mummies
<p>During an excavation beneath the Tarim Basin in western China, archaeologists were surprised to discover more than 100 mummified corpses that dated back 2,000 years. But a college professor named Victor Mair was downright stupefied when he came skull-to-skull with some of the blonde-haired and long-nosed Tarim mummies after they were dug up and put on display at a museum. So in 1993, Mair returned to collect DNA samples from the mummies. Test results ultimately validated his hunch that the bodies were of European genetic stock.</p> <p>While Ancient Chinese texts from as early as the first millennium B.C. describe groups of far-East dwelling Caucasian people, there is no mention of how or why they ended up there.</p>
The Voynich Manuscript
<p>The <a href="http://www.livescience.com/37737-voynich-manuscript-language-hoax.html">Voynich manuscript</a> just might be the most unreadable book in the world. The 500-year-old relic was discovered in 1912 at a library in Rome and consists of 240 pages of illustrations and writing in a language not known to anyone.</p> <p>Deciphering the text has eluded even the best cryptographers, leading some to dismiss the book as an entertaining but lengthy hoax. But a statistical analysis of the writing shows the manuscript does seem to follow the basic structure and laws of a working language.</p>
The Lost Roman Legion
<p>After the Parthians of Persia defeated an underachieving Roman army led by General Crassus, legend has it a small band of POWs wandered through the desert and eventually were rounded up by the Han military. First-century Chinese historian Ban Gu wrote an account of a confrontation with a strange army that fought in a "fish-scale formation" unique to Roman forces. An Oxford historian who compared ancient records claimed that the lost roman legion founded a small town near the Gobi desert named Liqian, which in Chinese translates to Rome.</p> <p>DNA tests are being conducted to settle that claim and hopefully explain some of the residents' green eyes, blond hair and fondness of bullfighting.</p>
Who Was Robin Hood?
<p>The real-life existence of a forest-dwelling altruistic bandit definitely seems more plausible then a legendary king with a magical sword. However, the historical manhunt for the real-life Robin Hood has turned up entire scrolls of possibilities. Candidates include a fugitive in Yorkshire by the name of Robert Hod, who went by Hobbehod as well as a Robert Hood of Wakefield. The list of suspects was also complicated by the name "Robin Hood" eventually becoming synonymous with being an outlaw. His identity would later get murkier as the tales' authors wove more characters such as Prince John and Richard the Lionheart into the story.</p>
The Carnac Stones
If erecting <a href="http://www.livescience.com/history/070130_ap_stonehenge_settlement.html">Stonehenge</a> seemed to have been a tremendous groan, think about how backbreaking it must have been the folks responsible for the Carnac stones. On the coast of Brittany in northwestern France are over 3,000 megalithic standing stones arranged in perfect lines and spread out over 12 kilometers. The local myth is that a Roman legion was on the march when the wizard Merlin turned them into stone. A more rational stab at an explanation by a researcher who studied the stones purported that the stones may have been an elaborate <a href="http://www.livescience.com/earthquakes/">earthquake</a> detector. The identity of the Neolithic people who built them is unknown.
Fall of the Minoans
As historians squabble over what caused the collapse of the <a href="http://www.livescience.com/history/070124_ap_palatine_hill.html">Roman Empire</a>, the fall of the Minoan empire has proved just as puzzling. Three and a half millenniums ago, life on Crete (the island residence of a mythical King and his man-eating beast) was disrupted by a <a href="http://www.livescience.com/history/060427_olive_volcano.html">volcanic eruption</a> from neighboring Thera Island. Clay tablets unearthed by archaeologists revealed that instead of folding, Minoans carried on for another 50 years before finally packing it in. Theories of what finally did them in include a scenario in which a blanket of volcanic ash devastated crops and one where a weakened society was left vulnerable to an eventual Greek takeover.
The Bog Bodies
Even CSI's best efforts wouldn't go very far in solving the mystery of the <a href="http://www.livescience.com/history/ap_050707_bog_people.html">bog bodies</a>. Hundreds of these ancient corpses have been discovered buried around the northern wetlands of Europe. Researchers who inspected the remains have reported tell-tale signs of <a href="http://www.livescience.com/history/top10_medieval_myths.html">torture</a> and medieval foul play. Such gruesome clues have some suspecting that the dead were the victims of <a href="http://www.livescience.com/history/070611_human_sacrifice.html">ritual sacrifice</a>.
Lost City of Helike
Greek writer Pausanias gave an account of how a great earthquake destroyed the city of Helike. Moments later, a <a href="http://www.livescience.com/tsunami/">tsunami</a> swept away what remained of the once-flourishing metropolis, which had been a worship center devoted to Poseidon, earth shaker and God of the sea. No trace of the legendary society existed outside of ancient Greek texts until 1861 when an archaeologist found a bronze coin with the unmistakable head of Poseidon. In 2001, a pair of archaeologists located the ruins of Helike beneath coastal mud and gravel. They are now working to unearth what some consider the "real" <a href="http://www.livescience.com/history/atlantis_theory_041115.html">Atlantis</a>.
Considered the other "Easter Island mystery," Rongorongo is an indecipherable hieroglyphic script used by the region's early inhabitants. While no other neighboring oceanic people possessed a written language, Rongorongo appeared mysteriously in the 1700s. However, the <a href="http://www.livescience.com/strangenews/060811_language_diversity.html">language</a> was lost—along with the best hopes for deciphering it—after early <a href="http://www.livescience.com/history/060309_easter_island.html">European colonizers</a> banned it because of ties to the islanders' pagan roots.