Phra Si Rattana Mahathat Temple is a major historical site blending Lopburi (Khmer) and Ayutthaya styles. It is famous for its tall, slender laterite main prang, which served as a prototype for early Ayutthaya prangs. The grounds house the Great Vihara, built under King Narai, featuring distinctive Western-style pointed-arch windows. Remaining stucco work on the gables and arches showcases the exquisite beauty of ancient Buddhist art. Located directly across from the Lopburi Railway Station, it is a key site for exploring Thailand's rich history.