The ancient city of Si Thep in Phetchabun Province was established as a city state between the 3rd and 5th centuries. Its early history has been derived from Chinese literature which identified the location of a Dvaravati culture of Mon people – one of three such settlements in the central plain. Following the Hindu phase, Buddhism began to flourish from the 6th century. The city was at its height during the Khmer Empire, but was abandoned during the 13th century, coinciding with the rise of Sukhothai and Ayutthaya as Thai-speaking centres of power. Si Thep was granted World Heritage status in 2023. The moated settlement containing a number of Khmer-style prangs and stupas extends over a large area, necessitating a golf buggy or trolley-bus for viewing.