To perform cyber security research on cyber-physical systems, the involvement of real physical systems and components is an obvious benefit. However, in the area of industrial control systems, limited accessibility to operational systems for experimentation motivates a growing trend for researchers to develop testbeds for security research. Comprehensive testbeds require a significant investment of resources to develop, which may not be the most efficient or feasible option for researchers. This work documents the physical and network architecture of a small but diverse testbed, comprising multiple PLC devices and physical processes. The contribution of this work is to facilitate research that requires capturing of the interactions between cyber systems and physical processes, and the effect of cyber-attacks on physical components and processes in realtime. A classification approach to better understand and communicate how testbeds are utilised in the research community is also proposed and provides context for this work.