What is Enlightenment? Few questions in the history of ideas can have given rise to more controversy, sustained over more than two centuries and extending into the furthest reaches of contemporary thought. In comparison, the ‘where’ of Enlightenment – the sites from which philosophes garnered their evidence, the settings in which their ideas took shape, the networks through which they were disseminated, the contexts in which they were interpreted – has received much less attention. It is not that these geographies have been altogether neglected. Distinctions between different ‘national’ Enlightenments (French, Scottish, English, and so on) are familiar, perhaps all too familiar, to historians of the eighteenth and early nineteenth centuries. At a smaller scale, it is difficult to imagine historical accounts of the Enlightenment world without some sort of tour of those paradigmatic sites – the coffee house, the botanic garden, the lecture theatre. There is a geography here, of sorts: but in truth it is often simply a stage for action, a passive background (sometimes ‘national’, sometimes ‘local’) to the real business of social and intellectual change. In recent years, however, intellectual historians in general, and historians of science in particular, have begun to pay more attention to these and many other sites, not simply as inert contexts but as vital components of the making and communication of new knowledge. Thus is a genuine geography of knowledge in the making.