I think Potsdam is a gorgeous city, and anyone who visits Berlin would be well rewarded by spending at least a day exploring its delights. It might encourage them to return and spend more time there.
Of its many diverse attractions, one of my favorites is the Dutch quarter, or Holländisches Viertel, right at the town centre. Since I first visited here in the year 2000 when it was still run-down after DDR-era neglect, the quarter has been massively renovated and is now one of the most stylish areas of Potsdam with an assortment of elegant restaurants, chic boutiques, unique artist's workshops (Atelier), and antique and artisan food shops. A bit pricey, but strolling around and admiring the architecture (one of the largest ensembles of Dutch town-architecture outside the Netherlands) costs nothing.
Here are a few photos I took of the area to give you an impression of it on a Spring day: