Roosevelt Island can be reached on the F train to Queens. It is a sliver of land between Manhattan and Queens, that has been undergoing redevelopment. Currently it houses some new condominiums and a gorgeous park in the southern end, the Roosevelt Memorial Park. It is intended that this park will celebrate the disability of Roosevelt (something that was hidden as a weakness during his time) so as to inspired those with disabilities. It also houses the ruins of a 19th century mental asylum, which is haunting! The island offers beautiful views of Manhattan, especially the Chrysler Building! The island also has a shuttle bus that takes you around, cost is 25c per adult.
On the way back take the aerial tram. Is covered by metro cards and gives a wonderful view of Manhattan and the river.
If you own or manage Roosevelt Island, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.