This is what is called a Spanish tower. In Luxembourg they have maps that give visitors a self guided tour itinerary. This maps show everything in the city except for the Spanish towers. I had to see them....see next photo. Luxembourg City, Luxembourg.
So on my quest to find these Spanish towers I had to climb a mountain, (I would call it a hill, they called it a mountain) crawl through a locked gate (clearly marked "Do not enter" in several languages thusly foiling my plan to be able to say "I am sorry, I don't speak the language") and avoid an elderly lady who had probably had a little too much to drink. But I got there! Luxembourg City, Luxembourg.