Mendips, Somerset, England

The first underland setting MacFarlane explores are the Mendip Hills in Southern England. The hills, composed largely of limestone, have been used by humans as burial sites for at least 10,000 years. They stretch almost thirty miles, ending at the sea near Bristol Channel. The hills are largely hollow and contain many different cave systems and burial sites. The hills are also the site of lead mining that stretches back 2,000 years, at least to the iron age. MacFarlane goes caving in the hills with a guide named Sean. "This is clearly a strong place -- and it has drawn humans to it for thousands of years," MacFarlane writes of one site in the hills (45). Inside the caves in the hills, MacFarlane feels claustrophobic. "Crouched in that bare space, my heart hammers warning in my ears," (47). "I reach out and place a hand on the black rock of...