Via a slack I’m on, I only just this morning became aware of the MegaProcessor, a 16-bit microprocessor with LEDs attached to all the gates and transistors, that is then blown up to the size of a room and mounted on walls so you can see it working.
Oh, and it plays Tetris.
Frankly, this thing is amazing, and I would love to see it in person one day. Here’s the computerphile video that let me know of its existence: