Source: The New York Times By DAVID W. DUNLAP The World Trade Center’s best-kept secret has finally come to light. It is an elevated park, slightly larger than an acre and 25 feet above Liberty Street, that will command a panoramic view of the National September 11 Memorial when it opens to the public, probably in 2015. Liberty Park, as it is called, is meant to offer a pleasant and accessible east-west crossing between the financial district and Battery Park City; to create a landscaped forecourt for the new St. Nicholas Greek Orthodox Church; to provide a gathering space for…