Rana Mitter goes underground to discover a world which long fed the human imagination and which fulfils all humanity's practical needs outside of food and yet which has become something we like to ignore, hide, conceal and forget. Counting the potential costs for all our futures, three enthusiasts for all that lies beneath, the engineer Professor Paul Younger from Glasgow University ; Ted Nield editor of the bi-monthly magazine Geoscientist and MIT's Rosalind Williams.

Professor Paul Younger from Glasgow University is the author of Water: All That Matters and Energy: All That Matters

Producer: Jacqueline Smith.