Just like us, our cats need exercise to stay healthy. The HolinDesign Standing Cat Wheel can help. It is an elegant exercise machine for your cats with a birch plywood and steel construction. It has a running surface of 370 x 27 cm (L x W). It can handle cats up to 25kg, so technically 2 cats can run on it together.
HolinDesign is selling these on Etsy. You can find out more here.