This is the "Schöner Brunnen", or "Beautiful Fountain" in the market square, and was one of the first landmarks we saw. It is a curiously decorated tower, covered in statues. According to this website, the statues represent the Seven Imperial Electors and nine ancient and mediaeval heroes. Around it is a unbelievably ornate iron fence, and woven in between the grillwork is a small brass ring. The local legend holds that if you make a wish and turn this ring three times it will come true.
Schöner Brunnen