This ancient walled plain is one of the most ancient features on the Moon. During the eons since its creation it has acquired many interesting features within its walls, including a conspicuous rille system, a mountain massif, and the large class 2 crater Fabricius.

Photo: António Cidadão. His Home Page of Astrophotography includes stereograms, animations, and "Seven Craters a Week" from his forthcoming photographic lunar atlas.