A major impact basin on the Moon, 930 km across, centred at −19° lat., 93° W long.; the central part is known as Mare Orientale. It is the best-preserved and probably the youngest of the large lunar basins, formed 3.8–3.9 billion years ago. At least three concentric rings of mountains can be seen within it. Long chains of secondary craters, caused by ejecta from the impact, extend to distances of more than 1000 km. Volcanic lava and small shield volcanoes cover part of the basin’s interior.
http://photojournal.jpl.nasa.gov/catalog/PIA13225