In Berlin, the son of Konrad Zuse is recreating the Z3 using modern relays. https://en.wikipedia.org/?title=Z3_(computer)

You can visit it in the museum. Forgot the name, has a plane on the roof.

He gave a talk when I was there, and afterwards, we where allowed to add some numbers on the computer. You can see the memory banks and hear the relais clicking and blinking.

An interesting fact is that it is a 32 bit floating point machine. Though when I was there he had some issues with synchronising the clocks, so it only did integers then.