The "Navigation.h" and "OsmPlacemarkData.h" header files (and possibly others) are not installed into /usr/include/marble upon running "make install". Thus, it seems to me that it is not possible to use these classes in a custom application. Reproducible: Always Steps to Reproduce: 1. Build Marble 16.04 by configuring with: cmake -DCMAKE_BUILD_TYPE=Release -DWITH_KF5=FALSE -DCMAKE_INSTALL_PREFIX=/usr -DQTONLY=ON -DBUILD_MARBLE_APPS=NO -DWITH_DESIGNER_PLUGIN=NO -DBUILD_MARBLE_TESTS=NO /path/to/marble 2. Try to compile a C++ program with #include <marble/Navigation.h> or #include <marble/OsmPlacemarkData.h> Actual Results: Compilation is failing. Expected Results: Compiled successfully.