Ayutthaya was the capital of the Kingdom of Siam from 1351 to 1767, when it was besieged and razed by the Burmese. In the ashes of the old kingdom came the new: the current Chakri Dynasty was founded soon thereafter, Ayutthaya being abandoned and the new capital established safely downriver in Bangkok.
Ayutthaya makes for a great day trip. A two-hour train ride, and you can see wondrous ruins of an old city.
A famous Buddha head, entwined by the roots of a bodhi tree (Ficus religiosa).