My favourite building was Grand Central Station, which has shops and restaurants inside, some of them on lower levels. The oyster bar has good reviews, but I don't 'do' shellfish so didn't try it out. Look out on the main concourse for the stars on the ceiling - allegedly back to front! There was a Starbucks inside the Trump Tower on 5th Avenue, which anyone could go to. It was up one floor (so the 2nd floor) and looked onto a lovely marble waterfall. If you're in New York on a Sunday then I would highly recommend the revolving restaurant on top of the Marriot hotel in Times Square. It does the most amazing Sunday buffet. Probably good at any time of the week, but I've only been for the Sunday buffet!