O’Neill cylinder

It is a space settlement concept proposed by American physicist Gerard K. O’Neill in his 1976 book

The High Frontier:

Human Colonies in Space. O’Neill proposed the colonization of space for the 21st century, using materials extracted from the Moon and later from asteroids

The Island Three design, better known as the O’Neill cylinder, consists of two counter-rotating cylinders. They are five miles (8.0 km) in diameter and are capable of being scaled up to twenty miles (32 km) long