In this paper, we discuss the development and proliferation of robot test arenas that provide tangible, realistic, and challenging environments for mobile robot researchers interested in urban search and rescue applications and other unstructured environments. These arenas allow direct comparison of robotic approaches, objective performance evaluation, and can ultimately provide a proving ground for field-able robotic systems such as those used at the World Trade Center collapse. International robot competitions using these arenas require robots to negotiate complex and collapsed structures, find simulated victims, and generate human readable maps of the environment. A performance metric is presented which quantifies several pertinent robot capabilities and produces an overall score used to evaluate and compare robotic implementations. Future directions for the arenas and the competitions are also discussed.