This shows Mare Fecunditatis (top right) with the roundish Mare Nectaris (near center) with the craters Theophilus and Cyrillus on the terminator. Lower down is the nearby crater Catharina. Further down at the center of is a curious straight feature called Rupes Altai. Rupes Altai is an escarpment in the lunar surface that is located in the southeastern quadrant of the Moon's near side. It is named for the Altai Mountains in Asia, and is the most prominent lunar escarpment. The selenographic coordinates of this feature are 24.3°S 22.6°E, and it has a length of about 427 km.