The former residence of Thai Kings, Bang Pa-In Palace was built way back in 1632. Also known as the Summer Palace, it was properly restored and constructed by King Chulalongkorn Rama V in the 1880s. The grounds mix European, Chinese and Thai architecture in one complex, most recognisably the Aisawan Thiphya-Art pavilion set on the lake. It's roughly 20 km from Ayutthaya's old town and commonly combined with a Historical Park visit as a single day trip.