Dyson sphere
From Tardis Wiki, the free Doctor Who reference
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)
