Vihara of the Reclining Buddha: Wat Yai Chai Mongkhon or the Great Monastery of Auspicious Victory is located off the city island in the southeastern area of Ayutthaya in present Phai Ling Sub-district.
In the past it bears other names as Wat Pa Kaeo or Wat Chao Phraya Thai and Wat Yai Chaiya Mongkhon.
In the year 1357 two princes of Ayutthaya (Chao Kaeo and Chao Thai) died of cholera. King Ramathibodhi I (r. 1350 - 1369) ordered the bodies of both princes to be exhumed and at the cremation site be established a monastery with a holy monument (stupa) and a preaching hall (viharn). He gave the monastery the name "Wat Pa Kaeo" or the Monastery of the Crystal Forest.
Ayutthaya is a city in Thailand about 80 kilometers north of Bangkok. It was capital of the Kingdom of Siam and a prosperous international trading port from 1350 until razed by the Burmese in 1767. The ruins of the old city now form the Ayutthaya Historical Park which is an archaeological site that contains palaces/Buddhist temples/monasteries and statues. The park is on an island between 3 rivers.