Scholars have, for nearly a century, theorized about the origins of the building known as the Cenacle on southwestern Mount Zion in Jerusalem. Some suggest that it represents the surviving remnants of either or both of the large-scale churches that once stood nearby: the Byzantine Hagia Sion or the Crusader Church of Saint Mary. Others, however, believe that the structure predates both of those edifices and represents a more ancient religious shrine. The majority of the latter believe that the Cenacle was originally a synagogue. But this identification is inconsistent with the architecture of the majority of pre-fourth-century synagogues discovered throughout Palestine and the Diaspora. Better examples for comparison might include the pagan shrines of antiquity, especially mithraea, or, as this paper will suggest, the early Christian hall churches of the second and third centuries. More definitive conclusions can only be obtained from further archaeological excavations in and around the structure itself.