Rendezvous with Rama (1973)

An apparently deserted alien cylinder passes through the Solar System, giving a human crew a limited chance to investigate. Clarke makes its interior feel like a landscape before it becomes an explanation: distance, light and unfamiliar machinery change how the explorers move and judge danger. The original Rama novel is an excellent starting point for discovery driven by observation. Its unanswered questions are part of the scale, so expect fascination without a complete account of the builders' intentions.