This paper proposes a novel tabletop display system for natural communication and flexible information sharing. The proposed system is specifically designed for integration of 2D and 3D user interfaces, using a multi-user stereoscopic display, IllusionHole. The proposed system takes awareness into consideration and provides both 2D and 3D information and user interfaces. On the display, a number of standard Windows desktop environments are provided as personal workspaces, as well as a shared workspace with a dedicated graphical user interface. In personal workspaces, users can simultaneously access existing applications and data, and exchange information between personal and shared workspaces. In this way, the proposed system can seamlessly integrate personal, shared, 2D and 3D workspaces with conventional user interfaces and effectively support communication and information sharing. To demonstrate capabilities of the proposed display system, a modeling application has been implemen...