[mkl]

They are Rings but smaller. Culture Rings are like Niven's Ringworld, and go all the way around a star, spinning around the star to simulate gravity. Culture orbitals are also ring-shaped and spinning to simulate gravity, but they're nowhere near as big (relatively speaking; still more surface area than Earth), and generally orbit a star more like a planet does. Culture Spheres are Dyson spheres.

[arethuza]

The size of an Orbital is dictated by day length and surface "gravity" - they are arguably more elegant than Niven style Rings which need a lot of extra stuff to generate day/night cycles (shadow squares?).

[mkl]

Yes. One book (The Player of Games?) gave enough numbers for me to do the calculations, and it matched about 24h and 1g.

[simonh]

I don't think the Culture builds rings or spheres themselves, but they exist and they are aware of them. There are civilizations in the galaxy considerably more advanced than the Culture.

[dodobirdlord]

I believe the Culture is credited as having creating the ring in Consider Phlebas.

[mkl]

Do you mean Vavatch, that was scheduled for destruction? That was Culture, but an Orbital.

[arethuza]

Vavatch was destroyed by a militarised Culture GSV but it wasn't "owned" by the Culture.

[p_l]

Vavatch was, IIRC (I'd have to search through) built by Culture, but since then ceded, similarly the ships that helped evacuate it