Something ring-shaped is a term used to describe two distinct shapes. A torus is a three-dimensional shape that is formed by rotating a circle around an axis that does not intersect the circle. It is often used to describe the shape of a doughnut. An ATOLL is a ring-shaped coral reef, island, or chain of islands formed by a coral reef surrounding a lagoon. Atolls are typically found in tropical regions and are formed over millions of years as the coral grows and the land subsides.