What are spinning black holes orbiting?

Question

I have seen depictions of spinning black holes with the "singularity" spinning around a center of rotation in a flat plane, or moving around an imaginary sphere. Is there anything in the centre or was that poor visualization on the artist's side?

Answer 1

There isn't anything in particular in the center. The black hole isn't orbiting, it is spinning (by which I mean it is rotating in and of itself). It is similar to how the Earth or a spinning top rotates about its axis: it isn't orbiting anything, just spinning.