The Subterranean power grid was an underground power grid responsible for providing energy to the city on Asuras. The grid most likely draws its energy from Zero Point Modules. When Dr. Rodney McKay's plan to attract all the Asuran nanites in one place created an enormous Godzilla-like mass of nanites, part of the grid was crushed by its weight, cutting the power to part of the city containing the central data core. (SGA: "Be All My Sins Remember'd")