What is your idea of an old German town? Heidelberg-like romanticist buildings, medieval wooden housings, Karlsruhe-like baroque or classicist cities? Freiburg has a rather large historic center with a cathedral/monastery church and gates, plus old quarters with lots of red sandstone.

Actually Freiburg has quarters with plenty of old town charm. And if that's not old town enough, you can always go to one of the smaller towns around, which should have plenty. It's an article that picks out and exaggerates one aspect of the city.