You cannot talk about a visit to Amsterdam without mentioning the red-light district. I really had no desire to visit, but my friend did and there were other stops on the way. I saw more than my share of street walkers in Detroit when I had a weekend job at a hospital in an area notorious for prossies. I'd be on my way to work and they would be on their way home.
So, here it is. Besides, what else could I do for the letter 'X' except 'x-rated'? Prostitution has been legal in Amsterdam since 1811. I think I should be congratulated for managing to get a shot without the crowds of strolling tourists. Not easy. And pictures into the windows themselves are not allowed.
You were expecting something else?
Bonus: X does not mark the spot - as seen in Germany: