1. A machine readable medium storing a program for execution by at least one processing unit, the program comprising sets of instructions for: receiving a set of road segments for a map region; for each road segment in the set, generating a geometry comprising a set of vertices that define a boundary for the road segment, wherein the geometries are included as part of a map tile for the map region, the map tiles for downloading to user devices that render map presentations using the geometries; and for a plurality of the vertices, storing data with the vertices that specifies for the device at least one aspect of rendering the road for the map presentation.