Hohenzollern
While you cannot take photos on the tour, you can get some interior shots of certain areas, especially the two chapels.  To the left is the earliest chapel, dating back before the 1200s.  Below is the chapel's interior, which is actually quite simplistic.
The other chapel is much more ornate within, bedecked with numerous flags commemorating victories in battles and other acts of the Kings of Prussia.
Below, a view into the main courtyard.  The chapels lie left and right of this photo... the earliest visible on the left, while the entrance to the newer one is to the right. 

Below left, a good specimen of a ceremonial culverin field piece.  Culverins and demiculverins are identifiable by their long, slender appearance compared to heavier guns, lying mid-range in the spectrum of firepower and utility.