Research aimed at securing the SCADA and ICS networks has taken off in the wake of Stuxnet. Unfortunately, it is difficult for researchers to fully capture the integration between cyber and physical components that is intrinsic to these systems. To enable researchers to perform network security experiments while taking into account the physical component of ICS networks, we propose the use of the ICS sandbox. The ICS sandbox uses the proven virtualized cluster approach to emulate SCADA networks with high fidelity. The virtualized cluster is interfaced with an electrical power flow simulator to integrate the physical component of an ICS network controlling electrical grid critical infrastructure without imposing scale constraints. Parts of the proposed sandbox were validated in a training session offered to industry professionals where a satisfaction survey indicated that hands-on session with the ICS sandbox provided significant training value to the participants that could not have been obtained in traditional training.