Geological Chronicle
Located near the northeastern limb of the Moon, Riemann is a lunar impact crater measuring 117.85 kilometers in diameter. Due to its position, the crater can just be observed edge-on when libration effects bring it into sight. It lies to the east-northeast of the large walled plain called Gauss, while the crater Vestine is situated to the southeast, beyond sight on the lunar far side.
The crater is a heavily battered and eroded formation that remains only a remnant of its former self, with an outer rim worn away in many places to form an irregular series of ridges in a rough circle. Its south-southwestern rim is overlain by Beals, a crater previously designated Riemann A before being renamed by the IAU. Several smaller craters lie along the western and southeast rim, while the eastern edge represents the most intact portion of the outer wall.
The interior floor contains a mixture of level terrain and rough ground where impacts have stirred up the surface. It is generally less rough across the eastern half, especially near the center. A small, bowl-shaped crater lies on the floor in the southeastern part of the interior, accompanied by the faint remnants of several other lesser craters. The feature is named after German mathematician G. F. Bernhard Riemann.