Topopolis

A topopolis is a proposed tube-shaped space habitat, rotating to produce artificial gravity via centrifugal force on the inner surface, which is extended into a loop around the local planet or star.

Topopoles can be looped several times around the local star, in a geometric figure known as a torus knot.

[1][2] In Matter, Iain M. Banks (2008)[3] depicts a topopolis that loops its system star many times in various braidings, and houses trillions of sapient residents.

The topopolis was so massive that stray gases from the system collected within the major spacing within the braids by gravitation alone, producing a slight atmosphere between the strands, that the author describes as a "haze".

Dennis E. Taylor (2020)[4] in the book Heaven’s River features an alien civilization inhabiting a topopolis.