First chamber -- Descending -- Part I. Seeing (Britain). Burial (Mendips, Somerset) ; Dark matter (Boulby, Yorkshire) ; The understorey (Epping Forest, London) -- Second chamber -- Part II. Hiding (Europe). Invisible cities (Paris) ; Starless rivers (The Carso, Italy) ; Hollow land (Slovenian highlands) -- Third chamber -- Part III. Haunting (The north). Red dancers (Lofotens, Norw