Dyson sphere

A Dyson Sphere takes the shape of a hollow sphere, with a sun at the center. The People lived in the inner shell of such a construct, known as the Worldsphere. (NA: The Also People, BNA: Walking to Babylon)

Romana and K-9 also had an adventure in a Dyson Sphere. (BBV: The Search)

Behind the scenes

 * The Dyson Sphere takes its name from the Earth physicist who first proposed it, Freeman Dyson.
 * Most fictional depictions of a Dyson Sphere, including those in Doctor Who, are, in fact, a Dyson Shell, something generally considered to be an engineering impossibility. An actual Dyson Sphere is a swarm of energy-collecting satellites around a star; the "sphere" is the shape of that swarm or bubble, not a solid object.