Phra Pathom Chedi in Nakhon Pathom is the tallest stupa in the world. The stupa dates back to AD 675, although archaeological excavations revealed that the area has been settled as early as the 4th century AD.
The Phra Pathom Chedi has been overbuilt a few times, and in each time, its height has been raised. In the 11th century, the chedi was overbuilt in the ancient Khmer style. However, when a severe drought hit the area, its population moved to another settlement called Nakhon Chaisi, leaving the abandoned chedi to the jungle.
A visit by the future King Mongkut, at that time serving his monkhood, provided a new lease of life to the chedi. Upon his coronation as Rama IV, King Mongkut ordered that the chedi be overbuilt and its height raised. Construction took place over a period of 17 years and was completed in 1870. At the same time, the Chedi Bucha canal was built to facilitate irrigation and transportation in the area. The population of Nakhon Chaisi was then ordered to move back and resettle around Nakhon Pathom, creating the town that we know of today.