The Luizi Structure, located in southeastern Congo, is a crater covered by grasses up to a meter (3 ft) high. The crater seen in this satellite image has about a 17 km (11 mi) diameter, with an intermittent ring about 5.2 km (3.2 mi) across, and a smaller, center ring about 2 km (1.2 mi) across. Around the perimeter of the crater, a rim rises approximately 300 to 350 m (980 to 1,150 ft) above the interior. In short, Luizi is a well-preserved, moderately sized, complex crater. Exactly when Luizi formed is difficult to answer. Researchers estimate that nearby rocks are 575 million years old – more than 300 million years older than the first dinosaurs. But besides knowing that the impact cannot be older than the rock layers it disrupted, geologists still cannot say when the impact occurred. Photo courtesy of NASA.