Crisium, also known as the Crisium basin, is a large impact crater located on the Moon. It measures about 555 kilometers (345 miles) in diameter and is one of the largest lunar basins. Formed by a significant asteroid impact, Crisium is characterized by its relatively smooth floor and surrounding ring of mountains, making it a prominent feature on the lunar surface. The basin is situated in the Mare Crisium, or Sea of Crises, which is a dark, basaltic plain formed by ancient volcanic activity. Crisium is of great interest to scientists because it provides insights into the Moon's geological history and the processes that shaped its surface.