Topping the list is the Apollo Crater, located within the Moon's South Pole-Aitken basin. With a staggering diameter of 492 kilometers (306 miles), its surface area exceeds that of many European nations, such as Ireland. When compared to Earth's largest active volcano, Mauna Loa in Hawaii, the Apollo Crater spans over 50 times the width. While terrestrial craters are often weathered by plate tectonics and erosion, Apollo stands as a 'giant fossil,' preserving the violent volcanic and impact history of the early Solar System in a scale simply impossible on our planet.