The navigation skills of monsoon sailing brought unprecedented interactions of ideas, cultures, and horizons across Buddhist Asia in the mediaeval period. The interconnected seaways from the Bay of Bengal through the South China Sea to the Sea of Japan underpin a variegated intellectual framework of political, artistic, architectural, and religious thought and practice that drew in travelling monks from disparate locales to take Buddhism beyond the monastic cloisters of the Indian subcontinent. The geographical pivot of this mobile network was the southeastern corner of Asia, with its flatlands and massifs, rivers and volcanoes, coasts and islands. What had been regarded by an early generation of colonial and post-colonial scholars as the peripheral or transit zone between the ancient cultural powerhouses of the regions roughly coinciding with the nation-states of ‘India’ and ‘China’, became in the 8th to the 14th centuries a flourishing centre of innovation and creativity in ritual, architecture, and iconography.