Niven combines two traditional science fiction plots, the exploration of an alien world and the investigation of an alien artifact in Ringworld. The first exploits escapes, fantastic sights, rousing battles and other familiar space opera devices to heighten visceral excitement while the second creates intellectual suspense by requiring the hero to analyze the products of an alien mind. The Ringworld is both a world and a machine, it provides adventure and requires thought. Thus the novel appeals to readers on both levels and demonstrates Niven's skills as a master of both adventure narrative and logically worked out scientific problems.