You know, in retrospect, if there was a “whirlpool” and a light then it would cause a flickering effect of letters spontaneously appearing in fragments all around the courtyard/CIA. To me that would be a fitting testament to cryptology’s efforts to decipher rapidly delivered fragments and pieces of text.
If Kryptos had been circular the effect would have been perfect but there would have been maintenance issues with the pool and lighting – perhaps this is the explanation for our S-shape?