One of the core features of Marble is the support for different maps (map themes in Marble speak) and different planets. Each of them can be viewed in different projections: Make the planet look like a globe using the Spherical projection or view it like a printed map in the Mercator projection. Map themes are configured in the Map View dialog in Marble. You find it in the tab bar on the left in the Desktop version. Marble’s mobile version on the Nokia N900 offers you to open the Map View dialog via the main application menu. The Map View dialog lets you choose a projection, the planet (celestial body) and a map theme. The rest of this tutorials explains these choices in detail. Marble supports about a dozen different planets. In the Map View dialog you can choose those planets where at least one map theme is installed for. The projection defines how the surface of the planet is presented on the screen. This can be a globe or some sort of a flat map. These maps are optimized for high zoom levels, showing many details on the street and city level. Some of them provide good country and even continent or space views, but that’s not their primary area of use. Need to find a route? Do you like hiking or biking? Want to explore the neighborhood? Pick one of these maps. The famous OpenStreetMap Mapnik layer. A general purpose map with useful information for the most common use cases. The map is identical to that shown on openstreetmap.org. The OpenStreetMap Osmarender layer. A general purpose map with useful information for the most common use cases. The map is identical to that selectable in the top-right toolbox on openstreetmap.org. Compared to the Mapnik layer (OpenStreetMap theme), this theme has more lively colors and presents some different data. The view from space looks better than that of Mapnik. On the other hand, Mapnik handles conflicting elements at the street level better. In Osmarender, icon sizes are less balanced and the z-order (stacking) is wrong for some elements. Labels overlap in densely packed areas. OpenStreetMap data presented for bikers. The map is identical to that selectable in the top-right toolbox on openstreetmap.org. A map theme optimized for hiking and biking, based on OpenStreetMap data. Includes a very nice hillshading layer that shows the terrain (activate it in the Legend tab). These map themes work fine in Marble from a technical point of view. The terms of service of the companies offering these maps, however, may prevent you from using it. If you want to use these map themes, you must install them manually. Make sure their terms of service allow you to use them within Marble. Source.