The setting builds suspense. Gadara and (Mark's) Gerasa were both part of the Decapolis, a primarily Gentile area with a large Jewish population (Jos. War 1.155). That tombs were unclean (for example, m. Nazir 3:5; 7:3; t. Baba Batra 1:10-11) and considered the usual haunts of demons and magic (PGM 101.1-3; Nineham 1977:153) increases the audience's suspicion that these demons are inordinately powerful-hence the narrative's opening suspense and christological impact.