Topopolis

A topopolis is a tube-like space habitat, rotating to produce artificial gravity via centrifugal force on the inner surface, which is extended into a loop around the local star. Topopoles can be looped several times around the local star, in a geometric figure known as a torus knot.

A topopolis can be compared to an O'Neill cylinder extended in length so that it encircles a star. A normal topopolis would be hundreds of millions of kilometers long and at least several kilometers in diameter. A topopolis with a big enough diameter can theoretically have multiple levels of concentric cylinders.