What Berlin got right is that they tried to get all of society into the same building. As in the well-off into the 1st floor (Belle Etage) the poor under the roof, but the idea was to have the doctor living in the same building as the plumber. I think that idea is key to having livable cities.

Of course a lotbof happened between these ideas and the situation now.

Heidelberg is of course pittoresque but not a city in the same league in size. Maybe Mannheim could be taken as a town planning model.