We are investigating methods to accelerate rendering of architectural walkthroughs. In this paper, we improve upon a cells and portals framework by using image-based rendering techniques. We first store a few reference images of the view through each portal. At run time, we replace portals with these images warped to the current viewpoint. We begin with a well-known scheme for handling the complexity of a model, whereby the boundaries of enclosed spaces (cells) are used to divide the total space, and views of geometry beyond the currently occupied space are limited to the openings (portals) by walls. Our system improves upon the replacement of portals with conventional textures because the warping removes the popping effect when switching between image samples and significantly reduces the number of image samples needed.