Beneath the grounds of one of America's most popular parks lies a mass grave where officials dumped the corpses of tens of thousands of poor and sick New Yorkers.
Washington Square is said to be one of the city's liveliest parks, popular with university students and dog walkers, but below its 10-acres lie the bodies of 20,000 people.
Research librarian Carmen Nigro wrote about the morbid secret in a blog post for the New York Public Library.
