Virtual Reality Artworks provide sophisticated user experiences but their development is a complex process. We describe the use of Intelligent Virtual Environments for VR Art. In this approach, virtual world behaviour is governed by a symbolic system. This supports news forms of experimentation with physical laws or with causality that we have termed Alternative Reality. In addition, basing world behaviour on a symbolic representation can facilitate collaboration between artists and scientists. We introduce the techniques behind Alternative Reality and illustrate these with examples from the prototype. We conclude by an outline of artistic work in progress using these techniques.