Geological Chronicle
Located near the south-west limb of the Moon, Bailly is the largest walled plain on the visible face of the Moon. Its position near the limb gives it a foreshortened appearance from the oblique viewing angle, and libration can limit visibility. The most favorable time for viewing this feature is near the full moon when the terminator is crossing the crater wall.
The formation is classified as a peak ring basin, having an interior topographic ring or a discontinuous ring of peaks with no central peak. In area it is comparable in size to a small mare, located north of the crater Le Gentil and east of Hausen. Observers have termed this walled plain a field of ruins due to its worn condition.
Bailly is part of the Nectarian system and is estimated to be more than 3 billion years old. Its uneven crater floor has remained free of basaltic flooding, covered with a multitude of ridges and craters and likely ejecta from Hausen crater. Peaks along its western walls reach heights of 3.0 to 3.7 km, while the eastern wall has peaks of up to 4.3 km.