Situated among magnificent scenery southwest of Wat Mahathat is Wat Si Sawai. Three prangs (pagodas) are surrounded by a laterite wall. Inside the wall, the viharn in the west, built of laterite, is separated from the main prang which was constructed in the Lop Buri or Hindu-style, but the other also constructed beside the prangs are Buddhist viharns.
The Crown Prince of that time who later become King Rama VI found a trace of the Hindu sculpture Sayomphu, the greatest Hindu God in this sanctuary. In his opinion, this ruin was once a Hindu shrine, but was later converted into a Buddhist monastery.