To the northwest of Santos-Dumont is a 90-km-wide system of rilles designated the Rimae Fresnel, being named for the Promontorium Fresnel that lies to the north of the crater. This last formation forms the northern end of the Montes Apenninus, and lies astride the gap that joins the Mare Imbrium to the west with the Mare Serenitatis to the east. To the southeast, in the valley past Mons Hadley, is the landing site of the Apollo 15 mission.