Duisburg's Rathaus is the main architectural anchor of the old centre, standing beside Salvatorkirche with a towered Neo-Renaissance confidence that contrasts with the city's industrial image. The building dates from the early 20th century, when Duisburg wanted a civic hall equal to its growing importance on the Rhine and Ruhr.
The exterior is the main reason to stop, especially if you are already visiting the church or walking between the Inner Harbour and the centre. It will not compete with the Ruhr's industrial cathedrals, but it helps explain Duisburg as a working city with older civic ambitions, not just ports, steel, and motorways.