Rupes Recta

Rupes Recta is a linear fault on the Moon, in the southeastern part of the Mare Nubium at 22°06′S 7°48′W / 22.1°S 7.8°W / -22.1; -7.8.

[1] This is the best-known escarpment on the Moon,[2][3] and is a popular target for amateur astronomers.

[3][4] When the sun illuminates the feature at an oblique angle at about day 8 of the Moon's orbit, the Rupes Recta casts a wide shadow that gives it the appearance of a steep cliff.

The fault has a length of 110 km, a typical width of 2–3 km, and a height of 240–300 m. Thus although it appears to be a vertical cliff in the lunar surface, in actuality the grade of the slope is relatively shallow.

At the southern end is a group of hills often called the "Stag's-Horn Mountains", although this name is not officially recognized by the IAU.