December 13 - 19, 2005: The Ayutthaya Historical Park, Ayutthaya. Formally known as Phra Nakhon Si Ayutthaya, the ancient city of Ayutthaya, was founded in 1350 by King U-Thong and remained the capital city of the Kingdom of Siam for 417 years, (from 1350 to 1767) ... During this time, 33 kings of various Siamese dynasties reigned in Ayutthaya ...Ayutthaya World Heritage Site Celebrations