Versatile, yet easy to use. Use Marble similar to a desktop globe; pan around and measure distances. At closer scale it becomes a world atlas, while OpenStreetMap takes you to street level. Search for places of interest, view Wikipedia articles, create routes by drag and drop and so much more.
Turn your smartphone into a fully featured navigation device. Marble supports worldwide offline search and offline routing with in-app download of data (free, of course!). Activate turn-by-turn navigation with voice guidance. Rumours say we're working on a tablet and an Android version.
At its heart, a software library powers the Marble applications -- also integrated in a wide variety of other projects like Digikam or the KDE workspaces. Using the Marble library in your project requires only C++, Qt and adherence to the LGPL 2.1. Last but not least you can extend Marble itself using plugins.