Coronae are geological formations found on several bodies within the Solar System, but they are especially prominent on the planet Venus. They originate when valcanic forces within the planet cause the surface to swell into a dome-like structure, which then collapses to leave a circular or elliptical pattern on the surface, a corona.
The largest of these coronae on Venus (and indeed the largest known in the Solar System) is Artemis Corona, extending southwards from the equatorial highlands of Aphrodite Terra. The corona forms a distinct ring-like structure some 2,600 km across (for comparison, on Earth the corona would encompass most of Western Europe or the continental United States).
A typical corona rises above the surrounding landscape, but Artemis Corona is an exception to this, so that it forms an irregular depression within its ring. Around the circumference of the corona runs a series of interconnected canyons, Artemis Chasma. Another deep chasm, Britomaris Chasma, runs across the northern floor of Artemis Corona, from its northern edge to it central regions. These chasms are thought to be the result of recent geological activity within and around the circle of the main corona formation.