When Lemuria, which went down first, almost 200 years before Atlantis sunk, they petitioned the Agharta Network. The Agharta Network is a network of subterranean cities that is guided by a city called Shambhala the Lesser (to distinguish it from Shambhala the Greater which is the etheric Shambhala over the Gobi Desert.) Shambhala the Lesser was created when the continent of Hyperborea was vacated after Earth lost her mantle and the planet started receiving radioactive waves