In the year 2270, with travel to the nearby planets well established, a bizarre discovery is made on Callisto, the eighth moon of Jupiter. Dozens upon dozens of strange wheeled artifacts—wheelers—are found buried beneath the icy surface. No one knows what they were used for and who left them in our solar system. The monks living in the asteroids who diligently watch for incoming rocks meanwhile notice something quite disturbing... and then there are the other moons of Jupiter, suddenly exhibiting rather bizarre behavior...

A wonderful hard SF novel from best-selling authors, perfect for those who like Ringworld, Rendezvous with Rama, etc.