Mount Longonot, 9,110 feet high, lies on the floor of the Great Rift Valley, thirty-five miles northwest of Nairobi. It is called after the apt Maasai name for it: Ol doinyo Loonongot, the mountain of many valleys and gullies. Of volcanic origin, the last eruption of a parasitic cone happened only 5,000 years ago. Steam still issues from the inside crater wall, indicating that it is now in a dormant phase but not yet extinct.