The Royal Palace of Ayutthaya, which is now known as the Old Palace, is situated next to the northern section of the city wall. King Borom Trailokanath turned the palace, which was built in 1350 by King U-Thong, the first sovereign of the kingdom, into a monastery (Wat Phra Si Sanpet) in 1448 when he declared the three grand wooden prasats built by King U-Thong as a phuttawat or religious zone. King Borom Trailokanath then extended the palace grounds further north towards the Lopburi River, which was then used as the city's moat. Several halls have been built since then. Places of interest in the Royal Palace.

Though founded in 1369, the ruins of Wat Phra Ram date mostly from its restoration in the 15th century. Its main feature is a well-proportioned prang situated on a stepped terrace adorned with chedis. Some of the prang's stucco decorations, including Buddha images in the walking and standing poses, still remain