This shows a timeslice of the path of a massive particle (with some specific initial position and velocity that gives a nice looking trajectory) around a spinning (Kerr) black hole (with parameters m=1, a=1/3). The black (very slightly squashed) sphere in the center represents the event horizon of the black hole.

I calculated the trajectory using mathematica (code in the notebook.nb file)by directly integrating the geodesic equations. Here's the piece of it in the sculpture, and here's a longer section. The particle will continue to orbit the black hole indefinitely, with the radius changing between a minimum and maximum value. In contrast to orbits around non-spinning black holes or stars/planets (which can only spin very slowly) the trajectory is three-dimensional, i.e. it doesn't just stay in one plane.

I imported the trajectory into Fusion 360, put a hollow tube around it, and printed it on my Prusa Mk3. Then I pushed some side glow fiber optic through the tube (that was the hardest part of the whole thing...). The base and black hole are also printed. In the base there is an attiny85 microcontroller, a potentiometer, and two WS2812b LEDs, powered via a micro usb socket. Here's a picture of the internals.

Twisting the black hole turns the potentiometer and changes the illumination between off, fixed color, color changing, and white.