Ride the F-Line from the buzz of Manhattan to the tranquillity of Roosevelt Island in the middle of the East river. With great views of Brooklyn and Manhattan from a different perspective, this is a side of NYC that is ignored by most the visitors to the city. Spend an hour or more walking through the gardens and parks of the derelict 1850s-built smallpox isolation hospital (designed by one of the greatest US architects, James Renwick Jr), then have drinks or lunch at one of the cafe bars before you head back to the whirl of Manhattan via the cable car. The return on the cable car is a real highlight, with great views of the city. An hour or two spent here will set you up for the rest of your visit to the city.