Manhattan is an Island

Roosevelt Island is also an island.
Can one island be part of another island? Advertising for a new Roosevelt Island building called The Octagon harps again and again on the fact that it is in Manhattan.
Joyce Cohen of The New York Times real estate blog The Walk-Through:

Sure, Roosevelt Island is politically part of Manhattan, but it has serious geographical issues. It lies in the middle of the East River. So don’t plan on walking to work.

And what’s Roosevelt Island like, anyway? A commenter on The Walk-Through says:

Roosevelt Island could be really, really cool, lifestyle-wise, but it’s not for the most part. It’s like living in North Korea – no commercial activity. One bad Gristedes, a grimy Chinese restaurant, a grimy pizza place, a grimy video-rental place, a grimy liquor store and one cafe/bar, Trellis, which actually should be given a chance. They’re pretty good and have a huge menu.
The PROS of Roosevelt Island are tennis and bike riding / walking / rollerblading and the views, which are amazing.
The CONS are those listed above and also that you would think that with a drawbridge to Queens, a subway line AND a tram, transportation would be pretty easy. Sometimes it’s not. During the Republican Convention they re-routed sea traffic under the drawbridge, and there was a thunderstorm that flooded the F tunnel under the East River and stopped the tram (fear of lightning strike). So for a few hours Roosevelt Island was REALLY an island – couldn’t get there except swimming or by boat.
The Octagon is at the far north of the island and it’s a good mile down to the subway station and farther to the tram. You have to depend on the Roosevelt Island bus system, which isn’t that reliable for a commute. Roosevelt Island isn’t exactly a “rush hour” mentality kind of place. You might think “I’ll walk, it’ll be good for me,” but wait until the winter.