The Frank Stella’s are the best. They are all over the city and they always look amazing. Two of my favorites are the Saatchi and Saatchi lobby (pictured) and the Citi Corp building in Midtown.
I think it takes place every Saturday morning to afternoon, vintage shopping while having a great view at the Manhattan skyline from the East River State park. You will find lots of vintage shops and warehouses around this area of Williamsburg.
My favorite place on Bedford Avenue, this bookstore has both new and used titles. If you're patient and look close enough, you can usually find a book that's worth more than they're asking. Not to mention their stellar selection of magazine titles. Good for design, art, photography, sociology, fiction, and everything in between.