Architectural design processes involve a variety of users with different levels of expertise such as architects, engineers, investors or end customers. An efficient process requires all involved parties to obtain a common understanding of the architectural models and problems to be discussed. This is an ambitious task as architects as well as other involved parties often need to work with two-dimensional (2D) floor plans. While these plans are meaningful and easy to interpret for professionals, ordinary users often face problems when deducing three-dimensional (3D) properties of a building. In this paper we address this problem by introducing an immersive virtual environment (VE) for collaborative exploration of virtual architectural models. We explore a layer-based visualization method, which stacks 2D floor plans in space providing a simple 3D impression without actually using a 3D model. Based on architectural work processes we developed a user interface including two registered representations of the same building. Our user interface allows an architect to specify a region of interest within a 3D overall view while other participants can follow his perspective in a second 2D view. In our setup the virtual building is displayed on two separate walls of an L-shaped projection system.