The metaDESK is a user interface platform demonstrating new interaction techniques we call “tangible user interfaces.” We explore the physical instantiation of interface elements from the graphical user interface paradigm, giving physical form to windows, icons, handles, menus, and controls. The design and implementation of the metaDESK display, sensor, and software architectures is discussed. A prototype application driving an interaction with geographical space, Tangible Geospace, is presented to demonstrate these concepts.