Making light-transmitting concrete sounds like an impossible and ridiculous task, but it turns out that it's actually a simple project with mesmerizingly beautiful results. You'll just need to grab some craft clay, concrete mix, and fiber optic wires.
Basically all you're doing is making sure that some fiber optic wires go through either end of a concrete disk by sticking them into craft clay and pouring the mixture over that setup. Once everything is dry and you trim the wires, you'll end up with this:
Shiny, pretty, and simple. Check out the linked Instructable for a picture-by-picture guide on replicating this project. [Instructables]