Worldsphere

From TARDIS Index File, the free Doctor Who reference.

The Worldsphere was the name of the home of The People.

It was a Dyson Sphere with a sun in the centre and a sphere built around the outside allowing all to live inside the sphere. It had a width of around 1 AU and was the home to over two trillion People. Inside the sphere was the planet Whynot. It was the largest artificially created object in its home galaxy. (BNA: Walking to Babylon)