Not only is this library one of the city's most beautiful—it opened to much fanfare in 2010—it's also Manhattan's first LEED-certified branch. Nearly every architectural feature, from the light wood floors to the circulation desk, is made from some type of recyclable material. Like the rest of the branch, the spacious children's room is both ultramodern yet classic and comfortable: Its elegant orange-red chairs and round tables, plus a storytime rug and orange bean bags, give the room a casual vibe. Our favorite element, however, is the sloping, padded reading nook under the glass-enclosed stone staircase that invites kids to ditch the notion that reading must be done in an upright position. 175 North End Ave at Murray St (212-790-3499, nypl.org).