Construct3D is a three dimensional geometric construction tool based on the collaborative augmented reality system "Studierstube". Our setup uses a stereoscopic head mounted display (HMD) and the Personal Interaction Panel(PIP) – a two-handed 3D interaction tool that simplifies 3D model interaction. Means of application in mathematics and geometry education at high school aswell as university level are being discussed. A pilot study summarizes the strengths and possible extensions of our system. Anecdotal evidence supports our claim that the use of Construct3D is easy to learn and encourages experimentation with geometric constructions.