An ancient Roman cemetery in northern England is home to 80 corpses of strong, muscular men who quite literally lost their heads. These decapitated skeletons leave behind a 2000-year-old archaeological mystery that spans all of Europe.

Silbury Hill is a huge artificial mound in southern England, about 130 feet high and covering five acres. Europe's largest artificial mound, it may have been built by the makers of Stonehenge...but they definitely weren't the last to use it.

The ultimate fate of the Neanderthals remains a major mystery. We know they went extinct, but why did they die out when our ancestors thrived? New evidence suggests massive, deadly volcanoes killed off the Neanderthals while completely sparing our ancestors.

Of all the continents, the human settlement of Oceania remains the most mysterious. We know that ancient humans walked across the now sunken continent of Sahul to reach Australia, and now some ancient trees reveal when they did it.

Vikings raided and plundered Ireland for much of the ninth century, eventually establishing two outposts. The fates of those two settlements couldn't be more different. The Dúbh Linn outpost became, well, Dublin, but the other was lost forever... until now.

Current genetic evidence says the ancestors of modern humans left Africa 60,000 years ago. But recently discovered stone tools in the Arabian peninsula and India suggest humans actually started exploring the world as much as 120,000 years ago.

The ancient world was home to many accomplished astronomers, included the Greeks, Mayans, Polynesians, and maybe Stonehenge's mysterious builders. But perhaps more than 10,000 years before these cultures looked to the sky, Australian Aborigines were the world's first stargazers.

For the living, doctor/patient confidentiality is considered a basic right, something violated by only the most ethically bankrupt. Yet King Tutankhamen's deadly diseases, incestuous habits, and missing penis make international headlines. Should researchers reveal all this intimate, embarrassing information?

Otzi the Iceman, the 5300-year-old frozen body discovered in the Alps in 1991, was thought to be a prehistoric murder victim. But a revolutionary map of his belongings overturns that theory, suggesting his "murder" scene is actually a ceremonial burial.

Even thousands of years ago, written messages were sent over long distances. Unfortunately, the concept of including your return address hadn't been invented yet, so we don't know where ancient letters came from (and which cultures were talking)...until now.