The earliest documented sighting of the mysterious creature swimming in Scotland's Loch Ness came in 1871, according to the monster's official website. Dozens of sightings have been logged since then, including the most recent in November 2011 when someone reported seeing a "slow moving hump" emerge from the murky depths of Loch Ness. Keystone/Getty Images
The twin-masted merchant vessel Mary Celeste set sail from New York on November 7, 1872, bound for Genoa, Italy. Its 10 passengers were not on board when it was found floating in the Strait of Gibraltar four weeks later. There were no signs of a struggle, and all of the boat's cargo was still on board. Its only lifeboat was missing. Keystone/Getty Images
The name Jack the Ripper came from a letter sent in 1888 to London police, purporting to be the killer of five prostitutes.
His true identity has never been proved. CARL DE SOUZA/AFP/Getty Images
The Shroud of Turin may be the most famous religious relic.
Some Christians believe the shroud, which appears to bear the imprint of a man's body, to be Jesus Christ's burial cloth. The body appears to have wounds that match those the Bible describes as having been suffered by Jesus on the cross. Many scholars contest the shroud's authenticity, saying it dates to the Middle Ages, when many purported biblical relics -- such as splinters from Jesus' cross -- surfaced across Europe. Antonio Calanni/AP
The Lockheed Electra, piloted by Amelia Earhart and Fred Noonan, flies over the Golden Gate Bridge at the start of a round-the-world flight on March 17, 1937. The two vanished during a similar flight in 1937. Keystone/Hulton Archive/Getty Images
A group of U.S. Navy Avenger planes, like the ones seen here in 1943, disappeared off the coast of southern Florida in December 1945. The planes were carrying 14 men. Thirteen more servicemen also vanished when they went to search for the missing fliers. That started the legend of the Bermuda Triangle. Other mysterious disappearances over the years have been linked to the Triangle, which is anchored by Bermuda, Florida and Puerto Rico. APIC
Stories of elusive giant, hairy human-like beasts have been told on several continents for centuries. In the Himalayan Mountains, it is known as the Yeti or the Abominable Snowman. North Americans have reported sightings of Big Foot or Sasquatch. Russians call theirs the Almasty. Topical Press Agency/Getty Images
The Los Angeles County coroner ruled that actress Marilyn Monroe's death in this room was a "probable suicide" from an overdose of barbiturates. Despite the official conclusion, questions have lingered for decades about Monroe's death in August 1962. She was 36. E. Murray/Fox Photos/Getty Images
U.S. President John F. Kennedy sits with the first lady in the back of a limousine November 22, 1963, in Dallas. Kennedy's assassination remains one of the most shocking events of the 20th century, and it's also one of its biggest mysteries. While a blue ribbon panel concluded there was only one gunman, a Gallup survey six decades later found that 60% of Americans don't believe that. Underwood & Underwood/Underwood Archives/Getty Images
Police sweep a field in Waterford Township, Michigan, in search of Jimmy Hoffa's body in July 1975. The ex-Teamsters boss was last seen that month outside a Detroit-area restaurant. His disappearance is a mystery that triggers occasional digs by FBI agents looking for his remains. Free Press/MCT /Landov
Actors Robert Wagner and Natalie Wood are seen on their boat The Splendour in October 1976. Wood's body was found floating off California's Catalina Island in November 1981. It was initially ruled an "accidental drowning," but the Los Angeles County coroner officially changed the death certificate last year to read "drowning and other undetermined factors." Steve Schapiro/Corbis