Text in English and German. Ludwig Persius (1803-1845) was a pupil of Karl Friedrich Schinkel and his closest assistant. Very little has been published about him to date. With the aim of providing an exhaustive documentation of all his work that is still in existence, the present volume now shows Persius' architectural work in its current condition in 180 photographs, with numerous as yet unpublished exterior and interior photographs including also many detailed views. Persius' architecture was moulded by the work of Schinkel. He was his site supervisor at the Hofgärtnerhaus in Charlottenhof, adopting its style inspired by Italian domestic architecture for his numerous villas with towers, which are still characteristic features of the Potsdam cityscape. He was a master of the disposition of building volumes and of tying buildings into the landscape. About 50 buildings have survived, including early industrial structures. Persius' work is to be found almost exclusively in Potsdam. King Friedrich Wilhelm IV appointed him to the post of an "Architect to the King", a title he shared only with Friedrich August Stüler. His best-known buildings are the Friedenskirche in Potsdam, the Heilandskirche in Sacrow and the so-called Mosque by the Havel bay in Potsdam, a steam-driven pump-house in the Moorish style for the fountains in the gardens of Sanssouci and an eminent example of the romantic and exotic transfiguration of a simple functional building.