That is too cool!
Isn't it fascinating? The table top versions have candles that, when lit, propel the propellers. I haven't seen this one at night, but I suspect the pillars light up.
Must be a relatively new addition, or just for Christmas. But then, I haven't been to Fredericksburg in a loooooong time.
It is part of a Christmas display in the park adjacent to the Vereins Kirche. The pyramids are found in many forms, but this is the largest one I've ever seen!