18. Poveglia, Italy

Nothing is more terrifying than the history behind Poveglia, Italy, and you would never want to go here even if it were allowed. The island located between Venice and Lido was used in the 1700s as a quarantine site for those who had the Bubonic plague, and they would go here to die basically. 

Then, in the 20th-century, Poveglia became an asylum for the mentally ill, and it was rumored that doctors would perform awful experiments on the patients. Today, the island is deserted for a good reason, because it is considered to be the most haunted place in Italy.