The Angkor Vihara Project, a collaborative campaign between the Archaeology Centre of the University of Toronto and APSARA National Authority, has sought to clarify both the religious transition and syncretism between Hindu and Mahayana Buddhist (Brahmano-Buddhist) temple (prasat) construction and Theravada (Sinhalese/Pali) Buddhist monastic construction. This unique religious phenomenon, one which proves pivotal to both ancient and modern Cambodian religious history, is thought to have occurred beginning in 13^th century, and features primarily within the civic-ceremonial citadel of Angkor Thom, where upwards of seventy prayer-halls/vihara (Khmer: preah vihear, known archaeologically as “Buddhist Terraces”) have been identified. Archaeological campaigns conducted by the Angkor Vihara Project between 2017-2023 have focused on the mapping, structural analysis, and excavation of these ancient sanctuaries alongside artifactual and radiometric analysis. Our results have not only established preah vihear as prominent and overwhelmingly abundant religious architectures from the 14^th century onwards, but also as focal points of community, social organization, and microcosms of a larger politico-religious order embedded within architecture in a similar manner to prasat. This presentation will primarily discuss the material results and formative interpretations generated from both campaigns, but will also briefly engage with previous studies exploring the relationship of preah vihear and different documented phases of Brahmano-Buddhist temple-conversion, important processes key to understanding the establishment of premodern Theravadin Cambodia.