Wat Arun Ratchawararam Ratchawaramahawihan is located on the western side of the Chao Phraya River, directly opposite Wat Phra Chetuphon Vimolmangklararm (Wat Pho). Wat Arun is an ancient temple believed to have been constructed during the Ayutthaya period. The exact year of its construction and the identity of its founder are unknown. Evidence suggests it was built before King Narai the Great (1656-1688), as indicated by the map of Thonburi created by Frenchmen Captain Claude de Forbin and engineer de Lamare during King Narai’s reign. This map shows the temple's sacred precincts, including the old ubosot (ordination hall) and vihara (assembly hall) in front of the main prang (stupa).