Mimas, one of Saturn's moons is the smallest object in the solar system to be round due to the pull of it's own gravitational force. It's impact crater Herschel (named after the moon's discoverer) is 81 miles across, it's walls approx 3.1 miles high, and it's central peak rises 3.7 miles from the crater floor (Mt. Everest is 4.1 miles high). The impact on this moon must have been immense as there are fractures on the far side that may have been created from shock waves from the impact traveling through the body of the moon. Often thought to be the inspiration for Star Wars' death star, the crater was in fact discovered after the creation of the film.