An ancient impact basin on the Moon over 1100 km across, centred at about +35° lat., 15 °W long. It is about 3.9 billion years old, and is the result of the largest impact on the Moon, which was nearly big enough to break the Moon apart. The Imbrium impact had far-reaching effects, sending ejected material over much of the Moon’s surface and creating deep fractures within it. Following the impact, a long period of lava flooding occurred through these fractures, creating the Mare Imbrium and submerging much of the Imbrium Basin itself and a large area outside it.