Between 1750 and 1850, the methods and function of imprisonment went through a transformation. Prisons became the centre of public disciplination. Their function was to transform delinquents into useful citizens. But how should the buildings be designed to achieve that aim? Which new technologies could be used? The birth of modern prisons was long-lasting, covering three generations. The author outlines this process and shows parallels to the developments in England and the United States.