Adding custom content to mapping applications

Digital maps can be composed of a series of image tiles that are selected based on the context of the map to be presented. Independently hosted tiles can comprise additional details that can be added to the map. A manifest can be created that describes the layers of map details composed of such independently hosted tiles. Externally referable mechanisms can, based on the manifest and map context, select tiles, from among the independently hosted tiles, that correspond to map tiles being displayed to a user. Subsequently, the mechanisms can instruct a browser, as specified in the manifest, to combine the map tiles and the independently hosted tiles to generate a more detailed map. Alternatively, customized mechanisms can generate map detail tiles in real-time, based on an exported map context. Also, controls instantiated by the browser can render three-dimensional images based on the combined map tiles.