This highly visited African attraction is the world’s largest inactive, unbroken and unfilled volcanic caldera. So what’s a caldera? A caldera is a large depression formed when a volcano erupts and collapses. During a volcanic eruption, magma present in the magma chamber underneath the volcano is expelled, often forcefully. National Geographic One of the Seven And more than that. The Ngorongoro Crater is listed as one of the seven natural wonders and is …