This research investigates King Mongkut?s vision of modernity as expressed through the medium of Phra Nakhon Kiri in Phetchaburi. King Mongkut used hierarchically traditional architecture as a means of bolstering national pride and legitimising claims to the right of kingship. Simultaneously, a political position of Siam as a modern state was manifested through European-Sino-Siamese hybrid architectural styles in the mid-nineteenth century. In addition, the bell-shaped pagoda style within the site complex reflected his religious reform directed at upgrading monastic practices and purifying the canon. His reformed Buddhist sect, Thammayut, is characterised as rational, intellectual, and humanistic. Such religious reform was integrated with scientific knowledge, which he had learned during his contact with Christian missionaries as a monk and later as king.