The reservoir in the Upper Derwent Valley west of Sheffield, completed in 1945, which drowned the villages of Derwent and Ashopton. Its two round bellmouth overflows and the Ashopton viaduct are landmarks, and the Derwent Dam above it was used by 617 Squadron to practise for the Dambusters raid in 1943. A favourite Sheffield day out for walking and cycling.
Wikipedia: Ladybower