This chapter explores virtual reality (VR) as a powerful tool for architectural experimentation. VR enables researchers to simulate environments with high fidelity, manipulate variables precisely, and collect data without the constraints of physical prototypes. The chapter discusses how VR enhances internal control while maintaining ecological realism, making it ideal for testing designs before construction. Examples include wayfinding studies, spatial comfort assessments, and safety simulations. Limitations such as user adaptation and equipment biases are also addressed. By leveraging VR, architects can test more scenarios efficiently, advancing evidence-based design through immersive experimentation.