4023 is most likely part of the eastern retaining wall for the road (abutted by glariat surface 4027) 2 midsize tufo ashlar blocks are topped by a large basalt boulder possibly of later origin. Abuts wall 4007 at a right angle though corner construction also missing (cut). ashlar blocks appear to be of similar construction of interior wall 4007, possibly enclosing the area designated at third room from the north. 4023 heavily truncated on both N and S sides, causes unknown.