A Habitat Ring is a large ring-shaped structure of a space station such as the Orbis and Ocellus. It generates artificial gravity via centripetal force from its constant rotation around a hub. This is the only way to experience Earth-like gravity in space, because there are no anti-gravity or gravity generators. The diameter of an Orbis habitat ring is about 4 km and generates Earth's surface gravity of 1 g. The smaller habitat ring has a diameter of 2 km with 0.5 gravity.
The ceiling of a habitat ring is transparent to let starlight into the living space. Inside is a breathable atmosphere and it looks like an infinite valley with upward slopes on both sides. The livable surface has green vegetation, forests, farms, houses, high-rise buildings and skyscrapers. People also live in the towering sidewalls. There are enormous storage bays at the rear of these stations to support the mega markets.
The habitat ring is based on the Stanford torus which was proposed by NASA in 1975. This design can house 10,000 to 140,000 permanent residents.