Ringworld

In the year 2850, on the eve of his 200th birthday, the cynical and world-weary human Louis Wu is recruited for an unprecedented interstellar expedition. His recruiter is Nessus, a two-headed alien Puppeteer, a notoriously cautious and manipulative species. The mission: to investigate a colossal, enigmatic artifact detected in interstellar space – a perfect, artificial ring, millions of miles in diameter, orbiting a distant star. Accompanying Louis and Nessus are Teela Brown, a genetically 'lucky' human woman whose lineage has been manipulated by the Puppeteers, and Speaker-to-Animals, a fierce and honorable Kzin, a tiger-like warrior race. Their journey takes them through unimaginable dangers and breathtaking wonders as they crash-land on the Ringworld itself. What they discover is a world of impossible scale and mystery, populated by diverse, often primitive, civilizations, all living on the inner surface of this colossal alien construction. The team must unravel the secrets of its creators and its current inhabitants, all while struggling to survive and find a way off the Ringworld.