The Scariest Places in the World (It’s Almost Halloween, People)

Espionage, torture, decapitation—it was all run-of-the-mill stuff during the 17th century when the Tower of London was used as a prison for those accused of treason. Among its most famous residents were Anne Boleyn, the second wife of Henry VIII, and the "Nine-Day Queen" Lady Jane Grey. Both were beheaded on the Tower Green and buried in the chapel, and it's said their headless ghosts roam the halls to this day. The Bloody Tower is thought to be the spot where the young sons of King Edward IV were murdered on orders from their uncle, while the Queen's Tower is reportedly haunted by the ghost of Arbella Stuart, the cousin of James I who was imprisoned and later murdered here.

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Ophidiophobes, this is your worst nightmare. Ninety miles off the coast of São Paulo, Ilha da Queimada Grande aka "Snake Island" is home to thousands of golden lancehead vipers (the largest concentration in the world). Legends loom large around these parts: two fisherman were once bitten here and found dead in a pool of their own blood, and a third was never found. The island is now off limits to everyone except the Brazilian navy who visits once a year to check up on the lighthouse, which was automated in the 1920s after the last keeper was also killed by a snake.

Built as a cemetery for the Capuchin friars in the mid-1500s, this catacomb became the eternal resting place for aristocrats in the 17th century, when it was discovered that bodies buried here had naturally mummified. It was believed to be an act of God, so the corpses were hung from the catacomb walls like relics. Today, five subterranean limestone corridors are lined with 2,000 skeletons, each with a label marking the name and date of death.

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There have been hundreds of ghost sightings at Edinburgh Castle, including a headless drummer boy, French and American prisoners of war, and even phantom dogs wandering the pet cemetery. In 2001, as part of the Edinburgh International Science Festival, a team of scientists spent ten days investigating the castle, with many reporting paranormal activity like sudden drops of temperature and the feeling of people tugging at their clothes. The castle isn't the only spooky part of this ancient city. Mary King's Close, an underground alleyway beneath the City Chambers, has been haunted since the 17th century, when residents who had the plague were sealed into their homes and left to die.

Called the “Bermuda Triangle” of Romania, the Hoia-Baciu Forest has earned a reputation for being one of the most ghostly on earth. What to expect when you're there? Headaches, rashes, scratches, and burns, as well as feelings of being watched. The place is also known for UFO sightings—in the 1960s two different photographers snapped images that showed disc-shaped objects hovering above the forest.

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The skeletons of 40,000 people were used to create this chapel beneath the Cemetery Church of All Saints in the town of Sedlec. It's the work of woodcarver Frantisek Rint, who was hired by the House of Schwarzenberg to organize the human bones interred at the ossuary in 1870. The centerpiece is a giant chandelier, which contains at least one of every bone in the human body. Just as creepy are the garlands made of skulls, six large bone pyramids, bone candelabras, and skull candleholders.

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Welcome to the most haunted house in America. Built in 1857, the earliest documented ghost here is "Yankee Jim," who was convicted of grand larceny and hung off a wagon on the spot where the house now exists. Almost as soon as the the Whaley family moved in, they reported hearing heavy footsteps. Today, museum visitors have seen windows mysteriously fly open, the spirit of family head Thomas Whaley roaming the upper landing, and a creepy little girl in the dining room. Legend has it she's the ghost of a friend of the Whaley children, who accidentally broke her neck on a clothesline in the back yard.

Opened in 1829, Philadelphia’s Eastern State Penitentiary was once the most famous prison in the world. It was the first to throw inmates into solitary confinement and housed notorious criminals like Al Capone. About 1,200 prisoners died there, and when it opened to the public in 1994 many visitors reported hearing strange noises: footsteps in the yards, wails in the corridors, disembodied laughter. Gluttons for a good scare can wander the 11-acre prison in the dark via ESP's "Terror Behind the Walls" nighttime experience.

This subterranean labyrinth holds the remains of roughly six million Parisians, whose bones were moved here from overcrowded cemeteries in the 18th century. Visitors can venture down 130 steps to the chilly tunnels and crypts lined with human bones to explore what's just a small portion of the nearly 200 miles of haunted passageways beneath the city's streets.