Ayutthaya

 Ayutthaya was once the capital of Thailand in the14th century.  For over 400 years, this was where the kings of Siam ruled, until 1767 when the Burmese invaded and destroyed much of the capital city. The Thais then moved their capital down towards Bangkok. 

Wat Phra Si Sanphet was once the largest temple complex in Ayutthaya, being rebuilt several times--namely because it was built on soft ground and the wats kept falling over. 

 This became a historical park in 1976 and part of UNSECO in 1991.  The Buddha head with the Spung tree growing around it has been used as one of the images for UNSECO ever since.