The Kaßberg is one of the largest surviving Gründerzeit and Jugendstil neighbourhoods in Germany — a dense quarter of late-19th and early-20th-century apartment buildings that escaped the wartime bombing that levelled much of the rest of the city. Street after street of decorated facades, bay windows, corner turrets, and carved sandstone doorways runs uphill to the west of the city centre.
It's not a museum piece. People live here; there are neighbourhood Kneipen, small shops, and bakeries. The best way to see it is simply to walk: take Weststraße as a spine and branch off on either side. The hill rises gradually and the views back towards the city centre improve as you go. The area has been attracting artists and people priced out of more fashionable German cities for years, and the mix of old fabric and low-key creative energy gives it a particular character that the city centre, for all its investment, doesn't quite replicate.