You're likely thinking of the Asteroid Belt, which is a region between Mars and Jupiter that contains millions of rocky objects, known as asteroids.

Here are some key facts about the Asteroid Belt:

* Location: It's situated between the orbits of Mars and Jupiter, roughly 2.2 to 3.2 astronomical units (AU) from the Sun.

* Composition: It's mainly composed of rocky asteroids, but it also contains some icy bodies.

* Origin: The Asteroid Belt likely formed from the remnants of the early solar system, material that never coalesced into a planet.

* Size: It's vast, stretching for hundreds of millions of kilometers. However, it's also very sparsely populated, with asteroids spread out over a large distance.

* Notable Asteroids: Some famous asteroids reside in the Belt, such as Ceres (the largest) and Vesta.

The Asteroid Belt isn't a solid ring, more like a sparse donut of rocks, with most of its mass concentrated in a few large asteroids.

Let me know if you have any other questions about the Asteroid Belt or the solar system!