Marble is a virtual globe application which allows the user to choose among the Earth, the Moon, Venus, Mars and other planets to display as a 3-D model. It is free software under the terms of the GNU LGPL, developed by KDE for use on personal computers and smart phones. It is written in C++ and uses Qt. Geothek is a fork of Marble adding a statistics module, pixel maps, and a 3D view. It is developed and used by Austrian publisher as atlas software for classrooms.