I know for sure that this is a standpipe*. Mostly because it says so, right there in plain sight. (Although to be fair, I’ve missed a lot of things that were also right there in plain sight, so that’s not a guarantee that I’ll see it.)
But besides that, look at those mortar joints. And that wavy shadow! It was a plethora o’ stuff to see.
Hot Springs, Arkansas
*How about that very lengthy Wikipedia article? Aren’t you just exhausted from all that reading?