And though millions—in some cases billions—of years of erosion have made it difficult to determine the exact size of the meteorites, there is a general scientific consensus around the world's largest craters, which mark the largest asteroid impacts. Here are the ten biggest known: 1. Vredefort Crater. Asteroid impact date: Estimated 2 billion years ago. Location: Free State, South Africa. Specs: Also known as the Vredefort Dome, the Vredefort crater has an estimated radius of 118 miles (190 kilometers), making it the world's largest known impact structure.