NACIS 2016 Presentation Nat Case, INCase, LLC Nathaniel Vaughn Kelso, Mapzen Mapzen's free and open Who's on First is, like most gazetteers, a big list of places with stable identifiers in a place hierarchy, but we're modeling a new way to think about gazetteers: a space where debate about a place is managed but not decided. Neighborhoods are one of the included place types. In compiling data for this layer, we have encountered challenges in the range of city political structures, the relationship of city to sub-city entities, and in the lack of documentation and data for neighborhoods in many places. Our starting point was shapes derived from Flickr's neighborhood tags, but we discovered additional serious issues with the original compilation of those tags. We'll approach (and not necessarily resolve) these questions in a tour through cities big and small in the United States and around the world showing challenges faced and the final result on the map and in search.