Take the four minute tram ride from Second Av & 59 Street and you can stroll around the trees and greenery and forget you are in the city for a while. If you are not in the mood for a walk, you can take the Roosevelt Island bus (50 cents) as far north as possible to the firehouse. Get off a little earlier at the supermarket if you need to buy sandwiches/drinks and proceed past Octagon Soccer Field. Then walk a little further, past the tennis courts and the rehab hospital till you get to the very northern end of the island, Lighthouse Park. A nice place to picnic (don't forget to clean up your trash!) and read the paper while you see the boats pass by. Roosevelt Island is a great place for bikes as very few cars are allowed on the island.