Poveglia Island, Italy
Large mats of peat can break free from lake bottoms, creating natural floating islands as big as an acre and as thick as 6 feet (2 meters). Some of these islands -- which have been found in California, Indiana, Maine, Ohio, Florida and Massachusetts -- sprout trees, which act as sails, ferrying the floating peat mats across the water [source: Belluck].
Some people believe that Poveglia Island is one of the most haunted places on Earth, and given its history, it's easy to see why. Located in the South Lagoon between the cities of Venice and Lido, the island was first inhabited in 421 by people fleeing invaders on the mainland [source: Travel Channel]. Residents had abandoned the island by 1348 when the Bubonic Plague hit Venice. Like many small, uninhabited islands, Poveglia was used to quarantine the dead and dying victims of the disease, many of whom were eventually burned on the island's giant pyres. More Venetians fell victim to Poveglia's grim fate in 1630, when the Black Death once again sickened many of the city's residents. This gruesome past had already inspired ghostly tales when Napoleon used the location to stash gunpowder and weapons in the early 19th century.
Poveglia only became creepier when, in the late 1800s, the island became an asylum for the mentally ill. Legend suggests that one of the hospital's doctors performed strange experiments on the patients in the 1930s, a task that eventually drove him to leap off of the asylum's bell tower. The last operation housed in the island's old hospital was a nursing home, which closed in 1975. The island has been abandoned since then, but locals claim that they still hear chiming from the bell tower, even though the bell was removed several decades ago.