History's Greatest Mysteries

Despite centuries of sightings and searches, one deep-sea monster remains unidentified; as evidence continues to mount, the mystery endures whether the Loch Ness monster exists.

In 1969, a serial killer taunts investigators with cryptic ciphers, leaving police and the public questioning his identity for over 50 years; new evidence and technology may finally be able to crack his code and discover who the Zodiac Killer is.

On November 22, 1963, President John F. Kennedy was assassinated, shaking the nation to its core; while an initial suspect is captured, many believe there's more to the story; investigators and amateur sleuths alike have been searching for answers.

In 1587, a group of settlers land off the coast of North Carolina on Roanoke Island to establish the first English Colony in America; a few years later, the 115 men, women and children vanish without a trace, leaving only cryptic clues.

In 1997, thousands of people across Phoenix witness a series of strange lights unlike anything they've ever seen; many think this could be one of the largest-scale UFO sightings in history, but there may be another explanation.

A holy relic from the Bible has been missing for over 2,000 years; while some believe the Ark of the Covenant was destroyed, many people think it's still out there; new clues could finally explain what happened.

In 1930, a New York Supreme Court justice with close ties to Tammany Hall, and future president Franklin Delano Roosevelt, steps out of a steakhouse and disappears; for decades, the case dominates mainstream media and remains unsolved.

One of history's most notorious pirates, Blackbeard, is said to have had a treasure worth millions of dollars; after centuries of searching, the legendary hoard remains missing.

An ancient mechanical device found on a 2000-year-old shipwreck has become known as the world's first computer; the machine is centuries more advanced than historians thought possible, but its origin and true purpose are shrouded in secrecy.