Room 151B was oriented north-south with a width of about 2 m and an undetermined length. Five strata were found: two floor surfaces and three feature-related deposits. Two small pit features were identified in the room. Given its position under the Great Kiva's antechamber, it was built and apparently used prior to construction of the Great Kiva. Few feature, strata, photographic, and documentary records are available for this room.