Big Dumb Object

An enormous artificial object built for reasons unknown, by builders unknown. Usually has many complex machines or mechanisms with obscure purposes. Often cosmically ancient, with builders long-passed.

Examples

• 1968 2001: A Space Odyssey

  The monoliths were created by a highly advanced civilizations, and until the end of the novel, have unknown purposes and motivations. When astronaut David Bowman enters the "Stargate" he sees brief glimpses of the massive artifacts, like spaceports, left over from previous stages of this civilization.

• 1970 Ringworld

  The Ringworld is a giant ring structure with a radius of about 1 AU inhabited to be explored by a landing party hired by a cowardly alien who wants to know if it poses any danger. It is inhabited by "fallen" civilizations, none of whom know its history.

• 1973 Rendezvous with Rama

  Perhaps the most famous example of this motif, the titular Rama is an extrasolar object that passes through the inner solar system. A team is dispatched to explore the inside of Rama, which spins to induce apparent gravity on its inside surface. A huge cylinder, Rama is at first frozen but begins to show signs of life as it nears the sun, becoming more temperamental and dangerous to the exploration team.

• 1979 Star Trek: The Motion Picture
• 1989 Hyperion

  The Time Tombs are incomprehensible and terrifying.