Ayutthaya is 76 kilometres north of Bangkok and boasts numerous magnificent ruins. The ruins indicate that Ayutthaya was one of Southeast Asia's (and probably the world's) most prosperous cities in the 17th Century and beyond. Phra Nakhon Si Ayutthaya Historical Park, a vast stretch of historical site in the heart of Ayutthaya city, has been a UNESCO World Heritage Site since December 13, 1991.