Giant rotating orbital habitat, built of woven diamondoid/buckyfibre cable; generally around 2000 km in diameter and 500 km deep, open to space so that air is retained through centrifugal motion (and a thin membrane).
When carbon nanotube buckyfibre cable became readily available through nanofacturing techniques, the size of rotating habitats could be increased considerably. The largest rotating habitats possible using this material can be somewhat more than one thousand kilometers in radius, depending on the mass of landscape included. In the Information Age Forrest Bishop proposed this design of ring-shaped, open ended habitat, with the atmosphere retained by centrifugal force and tall atmosphere walls.
The ring is constructed from a coil or weave of carbon nanotube buckytube, generally about 2000km in diameter and from 100km to 500km long. This coil, or weave, is used to reinforce the main bulk of the ring, which holds atmosphere, soil, water, rocky substrate and habitations. In most versions of the Bishop Ring design, the bulk of the atmosphere is retained by a tall atmosphere wall ranging in height from 50km to 200km. Even 200km high walls are not high enough to prevent gradual atmosphere loss, so a thin transparent membrane or airwall technology are used to cut atmospheric escape to negligible levels.
Generally the local star is permanently obscured from the point of view of someone standing on the ring-floor, to avoid constantly shifting illumination effects. This means the ring requires artificial lighting, generally provided by a central artificial sunlet called a luminaire. Power for this luminaire can be collected by photovoltaic cells on the outside of the ring; if the ring is distant from the star, the p-v arrays can be extended beyond the ring floor in both directions, and/or other sources of energy can be utilised.
One clade associated with the construction of Bishop Rings are the vac-spider species Hobo Sapiens, who can extrude a range of specialised buckyfibre filaments from their spinerettes.
Forrest Bishop's original concept can be found here
A paper on the illumination of Bishop Rings using luminaires can be found here (pdf file)