The unique geographical feature created by a volcanic eruption is a caldera. When a volcano erupts and empties its magma chamber, the ground collapses into the emptied space, forming a caldera. These features can vary greatly in size and shape, and they often fill with water, creating beautiful lakes. Calderas are significant in geology as they provide insights into volcanic activity and the Earth's geological history. Some calderas become popular tourist attractions due to their scenic beauty, such as Crater Lake in Oregon.