Nineteen arches of the South Bridge, built out from within in 1788 as workshops and storage. Within thirty years damp made them unusable and the poor moved in — no light, no drainage, no ventilation. Burke and Hare are thought to have worked here, selling bodies to anatomists. The vaults were filled in and only reopened in the 1980s; tours run through them now, and visitors' accounts are strikingly consistent.