For over four decades, a shortwave frequency has broadcast a monotonous buzz from Russia, day and night. Occasionally a voice cuts in, reads coded names and numbers — and vanishes. No one has ever officially explained why.

Since 1795, treasure hunters have poured fortunes — and six lives — into one hole in the ground off Nova Scotia. Nothing conclusive has ever come out of it.

In 1922, six people were killed on a remote Bavarian farm — days after the farmer found footprints in the snow leading to his house but never away from it. A century later, Germany's most haunting cold case is still open in all but name.

A 15th-century codex filled with impossible plants, bathing women and a script no one has ever decoded has defeated medieval scholars, WWII codebreakers and modern artificial intelligence alike.

In 1908, a blast hundreds of times more powerful than the Hiroshima bomb flattened some 80 million trees in Siberia — yet no crater and no fragments have ever been found.

A corroded lump of bronze pulled from a Greek shipwreck in 1901 turned out to be a 2,000-year-old astronomical computer — and no one knows who built it.

In 1590, John White returned to Roanoke Island to find 115 colonists gone — and a single word carved into a post. Modern archaeology may finally be closing in on where they went.

In the summer of 1518, hundreds of people in Strasbourg danced uncontrollably for weeks — many literally until they dropped. Five centuries later, no one is sure why.

In 1828 a teenager stumbled into Nuremberg claiming he had spent his whole life locked in a dark cell. Five years later he was dead — and two centuries of DNA science still cannot say who he was.

Hundreds of giant figures were etched into a Peruvian desert two thousand years ago. We know exactly how they were made. We still don't know why.