In the latest Granta podcast, Rachael Allen speaks to travel writer Robert Macfarlane. Macfarlane is the author of Mountains of the Mind, The Wild Places and most recently, The Old Ways. Macfarlane talks about ‘Underland’, his essay in Granta 124: Travel, which sees him exploring the underground caves of Karst country, and the different approaches writers take to show landscape through language. ‘When you're dealing with a geological context,’ says Macfarlane ‘its age exceeds your knowing, exceeds your comprehension. Deep time is dizzying and vertiginous.’