An uninhabited world in the Omicron Delta region, the amusement park planet was constructed long ago by a highly advanced alien race. Its purpose is to provide fun and recreation for space-traveling passersby. The planet is controlled by a computer which creates highly sophisticated robots to make visitors' fantasies real, based on their thoughts. The Enterprise visited the world in 2267, and returns there for shore leave for the crew in 2269 (stardate 5143.3). At that time, the crew discovers that the planet's Caretaker has passed away, and the semi-sentient Master Computer has developed a desire to grow beyond its world and join its fellow machines in the galaxy. The crew convinces it that it would be much more fulfilled if it kept to its original programming.