A monolithic view of Classic Maya society as dominated by divine rulers who inexplicably ceased to erect monuments with long-count dates during the ninth century is examined by reference to new information from Terminal Classic sites in the Sibun Valley of Belize. In this locale and elsewhere, the construction of circular one-room buildings — with striking associated artefacts — may be interpreted as signalling social tensions between the orthodoxy of Classic Maya divine rulers and the more heterodoxic beliefs and practices associated with circular structures built at the end of the Classic period. The round buildings are contextualized within the diversity of architectural expressions of the Sibun Valley and also within a peninsula-wide network of shrines. The chronological placement and character of the Sibun shrines is discussed by way of radiocarbon assays, obsidian sourced by INAA, and raw materials used for groundstone at sites throughout the valley. The presence of marine shell and speleothems — likely used as architectural adornment — found in close association with Sibun Valley round buildings permits discussion of the manner in which elements of the local effected a translation of heterodoxic tenets into vernacularized shrine architecture.