Artist inside a Fort?

Imagine walking by this Prussian Fort from the 1860's.
 Ludo says, "Jude,let's go inside and see some paintings."
 I thought he meant graffiti.  After walking through a dark
 hallway we entered into cavernous rooms.

Here, within these rooms, within this
abandoned Fort Diou, within the history
of war, art lives.

the colours are much more vibrant than they appear here

I have a whole new appreciation of the word gallery.