Interestingly, the Z3 was not meant to be Turing complete (by Zuse) (that is, he did not intend the functionality that Turing completeness describes. Living in Germany back then he did not know about Turing nor about the "on computable numbers" paper).

Only in 1998 did people find out that the Z3 was indeed Turing complete.

What's also impressive is that Zuse didn't know about Charles Babbage either.