Franklin D. Roosevelt Four Freedoms Park

Info via OHNY
Address: Southern most tip of Roosevelt Island

Though still under construction, this new park at the southern tip of Roosevelt Island is open to visit. Designed by the late Louis Kahn, the subject of the documentary My Architect, this park was designed over 40 years ago. Previously the coolest thing on this island was the abandoned smallpox asylum. Thankfully, although it's suffered some serious decay, the NYC Landmarks Preservation Committee designated the hospital a historic site and it will remain at the entrance to the new park.