Area 104 is bounded on the south by the Koobi Fora Ridge Road, on the west by a prominent fault that separates it from Area 100, on the north by the course of Il Iriyamang’werr, and on the east by the no longer used old road from points south to Ileret [3].

Sediments in central Area 104 are exposed along a series of sparsely vegetated badlands. Gullies provide most of the sedimentary exposure, as north/northwest trending ephemeral streams erode the landscape. The A2 marker bed is an important stratigraphic level in Area 104. This has been used as a key bed to correlate the sedimentary successions and subsequently infer dates for many of the hominin fossil remains in Area 104 and other Koobi Fora sites. It lies within the transitional zone for the Olduvai-Matuyama boundary and thus is effectively dated at ~1.78 Ma. On the other hand, dates for the White Tuff above the A2 marker range from 1.60 Ma to 1.63 Ma [2][4][5]. 

KNM-ER 3733 is the most important find in Area 104. It is a rare example of a relatively complete cranium of a Homo ergaster [6][7] - or to some researchers an "African Homo erectus" or a Homo erectus sensu lato. KNM-ER 3733 has an interpolated age of 1.63 Ma being stratigraphically located ~1.5m below the White Tuff. Several Paranthropus boisei fossils and a talus from a Homo sp. were also recovered from Area 104 at 4m below the A2 marker giving them a date of 1.78 Ma [6][2][8].