From the plains of the northern Oceanus Procellarum, in the northwest quadrant of the Moon's visible face, a region of highland some 200km across rises out of the ocean plain. This is the Aristarchus Plateau, an area of terrain broken by craters and deep lunar valleys. The most prominent of the craters in this region, and the crater that gives the plateau its name, is Aristarchus on the rise's southeastern edge.
The crater Aristarchus measures some forty kilometres in diameter, making it the largest crater in this part of the Moon's surface (though its near neighbour Herodotus is very nearly as large). Aristarchus is some 3km deep, and in its centre is a narrow, steep-sided central peak.
This crater was formed relatively recently in the Moon's history (it is estimated to be some 450 million years old, making it comparatively 'young' in these terms). Because of this, it is extremely well defined, with an unsually bright and reflective interior, and a system of rays spreading outward across Oceanus Procellarum from the crater itself.