Agartha is the name given in esoteric lore to a kingdom or civilisation that exists inside the earth. Conceptions vary, with some legends speaking of a vast network of tunnels and caverns. At the centre of the network is the city of Shambhala, somewhere below central Asia, ruled over by the Rigden Trakpa, the "King of the World". Other conceptions state that the earth is actually hollow and people live on the inner surface. The most extreme conception states that the earth is hollow, and we live on the inner surface, with the whole of the so-called universe existing in the central space, infinitely smaller than we suppose it to be.