Epoxy resin. Infused with something you think looks nice. Tint, glitter, bits of wood, marbles, flowers, you name it. Look up "epoxy resin projects" on youtube for creative ideas. Glue a board to the bottom of the counter and fill it with resin. For irony you could tint it to make it look like a sink full of water.
Soil. Seal it underneath using a vinyl board and silicone. Fill it with soil. Grow something creative. Daffodils, wheat grass, IDK it's oval you could make it a mini cricket pitch with real grass and little Lego players.
A black-hole-style parabolic coin roller, like they often have in museum lobbies.