A sacred building's overall form, a stupa, a mosque, a cathedral, rarely travels between religions intact. Its parts do, more often than either the buildings or their own descriptions usually say. A dome raised over a square or circular hall solves the same structural and symbolic problem in Roman temple building, in Byzantine church building and, after 1453, in the mosques the Ottomans built once Constantinople's Hagia Sophia had become one, its own great dome standing as both engineering source and captured symbol for architects who then raised domed mosques across their empire. A raised platform lifting the sacred precinct above the ground it sits on appears independently in Mesoamerican temple platforms, in Southeast Asian temple mounts and in the stepped temple towers of the ancient Near East, traditions with no route of contact between them arriving separately at the same solution to marking a place as set apart. A courtyard opening the building to the sky appears the same way, in temple, church and mosque plans that share no lineage.
Two different processes produce this pattern, and the parts themselves do not announce which one made them: direct transmission, an architect adapting a known solution across a conquest or a trade route, and independent invention, two traditions solving the same problem the same way without ever meeting. The building types above them keep their separate histories. The parts, catalogued here on their own, are where that convergence and that borrowing actually show.