Much is made of the limited space available on the surface of the Earth, especially for housing and especially in the urban areas to which people have tended to move from the countryside. This form of "lateral thinking" has been associated with much-regretted forms of urban sprawl and increasingly problematic access to adequate housing in urban areas. At the same time the urban sprawl has increased pressure on undeveloped areas, notably those provisionally set aside as "green belts". The question explored here is whether there is already a case for "voluminous thinking" -- or when such thinking may become relevant, if not essential. By this is meant the possibility of progressive development of subterranean property, in urban areas, notably at depths not previously considered, whether 100, 500, 1000 or 5000 metres -- or more.
underground real estate Earth vertical deep