The Devil's Triangle, or Bermuda Triangle, is a mysterious pocket of open water where perfectly functioning airplanes and ships appear to vanish without a trace. Over the past 35 years some 120 aircraft and 700 ships have inexplicably disappeared there in the midst of fine weather, resulting in the loss of hundreds of lives.

The first unusual incident in the Triangle was reported by Christopher Columbus himself when in 1492 he experienced unusual compass readings and saw strange lights in the sky while sailing through the area. The first recorded ship to disappear there was a 542-foot-long U.S. Navy Cargo ship, the USS Cyclops, en route from Brazil to Baltimore in 1918. The ship was last sighted near Barbados on March 5, and the Cyclops and its more than 300 crewmen were never seen again. President Woodrow Wilson reportedly said of the Cyclops, "only God and the sea know where the great ship has gone." Renowned aviator Charles Lindbergh reported that in 1928 he became disoriented in the Triangle for several hours; he eventually emerged unscathed but with no explanation for his malfunctioning compass and the heavy haze he encountered. But the most famous incident occurred in the Devil's Triangle in 1945 when five U.S. Navy bombers flying to the Bahamas, known as "Flight 19," disappeared. Manned by experienced pilots, all five planes reported malfunctioning compasses, then went off course, lost radio contact and vanished.

The enigmatic Triangle has been known by a number of other names, including the Triangle of Death, the Sea of Doom and the Graveyard of the Atlantic.

Many of the theories surrounding the mysteries of Devil's Triangle involve the supernatural. Some place the blame for the disappearances of aircraft and ships on the presence of UFOs. Many UFO sightings have been reported in the area, and in 1980 a pilot radioed in that an unidentified object was approaching his plane. The plane then lost radio contact and was never seen again. The UFO theory is even featured in the Stephen Spielberg film Close Encounters of the Third Kind, in which aliens abduct the lost pilots of Flight 19. Some maintain that a U.S. Navy facility called AUTEC (Atlantic Undersea Test and Evaluation Center), which is located on Andros Island in the Bahamas, is involved in UFO research and that its activity is behind the strange disappearances in the Devil's Triangle. Others believe that deep beneath the Devil's Triangle lies the lost island of Atlantis, which emits unusual energy rays that affect vessels' ability to navigate. Still others have postulated that the Triangle is some kind of black hole.

More scientific explanations include one that holds that giant gaseous bubbles of methane erupt out of solid deposits on the sea floor in the area. Experiments have shown that if ships collide with these massive bubbles, they will sink. If the methane rises into the air it could even ignite and explode passing aircraft. Another theory posits that enormous "rogue waves" generating as much as 20,000 pounds of pressure per square inch, suddenly overcome and sink ships traversing the Triangle. An even more plausible theory involves the Gulf Stream, which can produce sudden, turbulent waters that may not only sink ships, but sweep away all evidence of wrecks.

Some say that the mystery of Devil's Triangle is actually not a mystery at all, but a legend based on a few coincidental and unusual accidents. These theorists point to the fact that the statistical frequency of unexplained incidents is no greater in the Devil's Triangle than in other parts of the world.

In 1888, a string of gruesome murders gripped the city of London. The unidentified murderer, who came be known as Jack the Ripper, sliced the throats of five unsuspecting prostitutes, mutilating all except one of them. Jack the Ripper's first victim was Mary Ann Nichols, whom he killed on the night of August 31, 1888. The mother of five children, Nichols was found dead with her throat slit and her stomach mutilated. A week later, on September 8, 1888, Jack the Ripper struck again, murdering Annie Chapman, a 47-year-old prostitute who was found dead and disemboweled. On September 30, Jack the Ripper killed his third and fourth victims: He cut the throat of Elizabeth Stride but did not touch her body--investigators believed he was interrupted before he could. Later that night he killed Catherine Eddowes and savagely mutilated her body and face.

Investigators initially made no headway in discovering the perpetrator of the grisly crimes, which were known popularly as the “Whitechapel murders,” after the location in which they occurred. Then on September 27 a news agency received a letter that began “Dear Boss.” It was written in red ink and signed “Jack the Ripper”; the pseudonym stuck. A few days later a postcard smeared with blood arrived at the same location, and soon after, a deluge of letters claiming to be written by Jack the Ripper were sent to the police and the press. One letter, sent on October 16 to the Mile End Vigilance Committee, a group of non-professionals convened to help solve the murders, arrived with a piece of a human kidney, which the author claimed belonged to Catherine Eddowes. The fact that the killer had the surgical skill to remove a kidney caused investigators to suspect that he might be a doctor, but they still made no progress on the case. The last murder thought to be tied to Jack the Ripper was Mary Jane Kelly, whom he killed on the night of November 9. To this day, Jack the Ripper has not been identified.

Stonehenge is a prehistoric archaeological site located in southern England. Built about 4,000 years ago, this circular arrangement of large, monumental stones is one of the world's oldest mysteries. Although archaeologists and historians have mostly reconstructed how the massive stone structure was built, they still do not know why it was built. Its purpose has perplexed and intrigued historians and tourists alike for hundreds of years.

Archaeologists believe that Stonehenge was built in three stages beginning around 3100 B.C. Some believe the construction of Stonehenge was never completed as originally planned, and that had it been finished, it would have been made up five trilithons, which are massive monolithic post-and-lintel structures, made of sarsen stone, an extremely hard sandstone that occurs naturally in the area. The trilithons were composed of two large vertical sarsen stones, supporting a large horizontal sarsen stone across the top. It is believed these were then surrounded by a circle of 30 large upright stone posts capped by stone lintels that formed a continuous ring. Inside the outer circle of sarsen stones was a circle of bluestones, and another circle of smaller bluestones in a horseshoe shape stood inside the five trilithons. Bluestone is a blue-black stone native to the Presali Mountains in South Wales. The entire monument was surrounded by a circular bank and ditch.

Only some of the bluestones remain today, and only 17 of the 30 upright stones remain. Over its four millennia of existence, during which it faced plundering and a good deal of weathering, Stonehenge has come into ruin and is only a shadow of its former self. Still, it is probably the world's most important example of prehistoric architecture, and it attracts hundreds of thousands of tourists every year, not only because of its historic importance but also because of the mystery surrounding its use.

For thousands of years the mysterious purpose of Stonehenge has intrigued historians, archaeologists and laypersons, who have advanced numerous theories through the years—some based on historical findings and others more fantastic in nature.

In 1655, Inigo Jones, a royal surveyor, wrote the first book on the subject of Stonehenge, arguing that Stonehenge was the work of the Romans. Shortly after, Walter Charleton wrote a response, disputing Jones' theory and instead claiming that Stonehenge was of Danish origin. Neither theory held water for long, but the dispute was emblematic of the many claims and counter-claims that have been advanced over the years about the origin and purpose of Stonehenge.

Another early theory held that Stonehenge was a Druid temple, but that claim was discounted once historians confirmed that Stonehenge predated the rise of the Druids by about a thousand years. (Nonetheless, present-day Druids still gather near Stonehenge to celebrate the solstice.) After the first excavations of Stonehenge in the early 20th century, archaeologists came to learn more about the site and the people who built it. One new theory held that Stonehenge was a place of worship for the primitive people who constructed it. Another proposed that it was a prehistoric celestial observatory. In 1966 Gerald Hawkins, a British astronomer, developed a theory that Stonehenge was actually a primitive computer that predicted the solstices and solar and lunar eclipses. Some discounted Hawkins' findings, but it resonated with others, and the field of “astro-archaeology,” the study of the early history of astronomy, was born. More recently, cremated human remains were discovered at the site, and archaeologists have begun to theorize that Stonehenge was a burial site for the elites of the prehistoric people of the area, although that would not necessarily preclude the possibility that the monument had other purposes.

The world's understanding of Stonehenge has evolved and morphed through time, and has been dependent on both scientific findings and human imagination. As the archaeologist Jacquetta Hawkes once said, every age “has the Stonehenge it deserves—or desires.”

The history of Alcatraz prison began in 1861 when the U.S. military converted a military fortress on the island into a jail to house Confederate sympathizers. In 1934 the military handed the prison over to the Department of Justice, and for 29 years it served as a maximum-security civilian prison for America's most dangerous offenders. Also known as "The Rock," because of the 12 acres of solid rock on which it was built, the prison housed a number of well-known offenders in its history. Gangster Al Capone was transferred to the isolated penitentiary in 1934 after he was discovered bribing guards at a federal prison in Atlanta. Another famous inmate was murderer Robert Stroud, known as the "Birdman of Alcatraz." Imprisoned on the island prison from 1942 to 1959, Stroud earned his nickname because he became fascinated with birds and wrote an important book on the subject while in prison.

Because of its island location and tight security, few escape attempts from Alcatraz were ever made, and it is believed that none was successful. The most famous attempt was known as the "Battle at Alcatraz," which started with a six-man escape but turned into a violent uprising.

The island prison was shut down in March 1963 after critics called its isolation cells cruel and inhumane and its island location made it too costly to maintain. In 1972 Alcatraz Island became part of the Golden Gate National Recreation Area and has been a popular tourist destination ever since. Some tourists are even lured to the island for the fabled stories of hauntings at the old prison. Witnesses say they have seen and heard the ghosts of its notorious prisoners emanating from the old penitentiary building.

In Alcatraz's 29-year history, only 14 escape attempts were made, and 23 of the 36 escapees were quickly captured. Six were shot before they reached the water, and two drowned in the San Francisco Bay. Five other escapees were never found. Three of these, brothers Clarence and John Anglin and inmate Frank Morris, who were all convicted bank robbers, escaped in 1962, but investigators never discovered what happened to them. Their complicated escape plan probably took months to plan. The three men were first discovered missing when prison guards found their cells empty. They had placed dummies in their beds and built a makeshift raft out of raincoats. Some maintain they escaped safely, but many believe that they likely attempted to reach Angel Island, two miles away, but would not have been able to survive San Francisco Bay's dangerously cold waters. The FBI investigated the escape extensively and concluded that the three men had died, although their bodies were never found. Their famous escape remains part of the lore of Alcatraz, and Clint Eastwood's character in Escape from Alcatraz was based on the escape's mastermind Frank Morris.

The Anglin/Morris escape is not the only mystery surrounding Alcatraz: Ever since the prison was shut down in 1963, there have been reports of ghost sightings and strange noises coming from the old building. Witnesses believe the spirits of the imprisoned men of Alcatraz may be haunting the prison. Some have even heard music echoing through the abandoned prison that sounds like a banjo, the instrument that Al Capone played during his prison stay.

In the late 1960s, an unidentified serial killer who called himself "the Zodiac" murdered five people in Northern California. The mystery killer's first confirmed victims were 17-year-old David Farraday and 16-year-old Betty Lou Jensen, who were parked in their car in Benicia, California, on a December night in 1968. The Zodiac killer pulled up beside them and shot the young couple dead. Seven months later, on July 4, 1969, an unidentified individual approached another young couple in a parked car, this time in Blue Rock Springs Park in Vallejo, California. The man shone a bright light into the car and then opened fire. Darlene Ferrin, 22, was killed on the spot, but her boyfriend 19-year-old Michael Mageau, survived. An hour later a man called the police and confessed to the murder but did not reveal his identity. He then began writing eerie letters to local newspapers, in which he took credit for the murders. He signed the letters with a scrawled circle with a cross in the middle of it. Some of these letters contained four mysterious ciphers, or coded messages. The messages stumped investigators, but a California couple cracked one of them when it was printed in a local newspaper. It read in part: "I like killing people because it is so much fun." The other three coded messages remain unbroken to this day.

On September 27, 1969 the Zodiac killer attacked yet another couple parked in a car near Lake Berryessa in Napa County. He again managed to kill only one of the victims, 22-year-old Cecelia Shepard; the young man with her, 20-year-old Brian Hartnell, survived. The victims and circumstances were similar, but this time the Zodiac killer used a different weapon: a knife instead of a gun. But he left behind a message--his signature circle with a cross and the dates of the previous attacks--leading investigators to conclude that it was the same killer.

The Zodiac's killer's last confirmed murder occurred in San Francisco on October 11, 1969. The murderer hailed a taxi and then shot the cabbie, Paul Stine, in the back of the head. He cut off a piece of the victim's shirt and sent it to the San Francisco Chronicle two days later. With it, he sent a letter with his signature symbol, threatening to kill a school bus full of children. The threat sent the public into a frenzy, but nothing ever came of it.

The press received a final letter from the Zodiac killer in 1974, and he was never heard from again. A number of serious suspects were investigated over the years, but the identity of the Zodiac killer was never confirmed. The Zodiac's gruesome, random murders captured the public's imagination, and even inspired the 1971 film Dirty Harry, starring Clint Eastwood.

The identity of the Zodiac killer has eluded police for 40 years. Since the first murder, investigators have invested significant resources into the case, examining evidence, questioning witnesses, poring over the cryptic codes and in the end ruling out some 2,000 potential suspects.

With the help of five eyewitnesses of the cab driver's murder, police constructed a composite sketch of what they think the Zodiac looked like. The resulting picture of a man with glasses and a crew cut never helped locate him. Code breakers for the CIA, the FBI and naval intelligence toiled over the three unbroken codes but have so far been unable to crack them. One of the three remaining codes has been in the top 10 of the FBI's Cryptanalysis Unit's list of unbroken codes for 40 years.

Among the many suspects considered, including serial killer Ted Bundy and Unabomber Ted Kaczynski, one of those scrutinized most closely was Arthur Leigh Allen (1933-1992), a schoolteacher who had been convicted and imprisoned on child molestation charges. But in 2002, DNA testing showed that Allen was not the Zodiac killer. Over the years hundreds of people have claimed to know the identity of the Zodiac, and as recently as April 2009, a California woman held a press conference in which she announced that her deceased father, Guy Ward Hendrickson, a carpenter from Santa Ana, was the Zodiac killer. Police investigated the claim, but initial reports suggested this was yet another false lead.

The elusiveness of the Zodiac killer has inspired thousands of amateur sleuths around the world to follow the case, and its many suspects, closely. Robert Graysmith, a former cartoonist for the San Francisco Chronicle followed the case with particular scrutiny and even wrote a book called Zodiac in 1976, upon which a 2007 film of the same name was based.