It is 89% the mean equatorial diameter of 569 km (354 mi), making it one of the largest craters in the Solar System, and at 75°S latitude, covers most of the southern hemisphere.

Rheasilvia was discovered in Hubble Space Telescope images in 1997,[4] but was not named until the arrival of the Dawn spacecraft in 2011.

It is named after Rhea Silvia, a mythological vestal virgin and mother of the founders of Rome, Romulus and Remus.

This basin consists of undulating terrain and a central mound almost 200 km (120 mi) in diameter, which rises 20–25 km (12–16 mi; 66,000–82,000 ft) from its base,[3][2] one of the tallest known mountains in the Solar System, and possibly formed due to a planetary scale impact.

[6] Spectroscopic analyses of Hubble images have shown that this crater has penetrated deep through several distinct layers of the crust, and possibly into the mantle, as indicated by spectral signatures of olivine.