Spiegel might be my favorite US based dive. I lament any year I don't get at least a double dip on it. I'm sure others have reasons why they prefer another or why other FL artificial reefs are better, but for some reason I have a special spot in my heart for this one. For my first dive on it, The Chairman crewed the boat I was on (he had a head cold and couldn't dive so he offered to crew). I joined Scubaboard a couple of days later. I have had Capt. Jim as the captain of the boat going to the Spiegel multiple times and wish I had picked his brain a bit during those SIs.
Reading the Wikipedia page informative and looking at the picture of it and trying to orient to it's current state is a nice way to spend some time.