Others have also suggested this. See, for example, Duane W. Roller, The Building Program of Herod the Great (Berkeley: University of California Press, 1998), p. 167: “It seems inconceivable that the upper structure should be anything other than Herod’s tomb. Although constructed in the style of a royal villa, the large round tower on the east—which intersects the villa peristyle—dominates the structure. It is strikingly remindful of cylindrical tombs in Rome.”