This document discusses how public libraries can adapt to serve "long tail" niche interests in cities. It defines the long tail concept of serving many small niche markets and how this is partially affecting physical product distribution. Cities can serve both mainstream and niche interests through their extensive resources and specialized areas. The document examines three case studies of large urban public libraries - in Bologna, London, and Barcelona - that aim to satisfy diverse user needs through large collections, variety of spaces and services, and a focus on certain niches. It concludes that both central and local libraries must find a clear role, with central locations emphasizing comprehensive resources and local branches focusing on specific interests or partnerships.