Dams are still often seen as a source of 'clean energy', even though they have disastrous environmental and social consequences. Even the promise of climate-friendly energy production is not fulfilled, because in fact dams are a major source of greenhouse gas emissions - 'clean energy' turns out to be a driver of both climate change and social conflict. Nevertheless, mega-dams in particular have continued to advance globally in recent years. An interdisciplinary special issue of the journal Sustainable Development, now fully open access, is dedicated to dams as a social phenomenon. It vividly shows the profound social hopes and conflicts associated with large dams.