The Phra Chedi, or Stupa, is the most venerated religious structure of Buddhism. Originally, it enshrined relics of Lord Buddha. Later, it contained relics of holy men or kings, and now has become a religious symbol much like the cross. A Stupa was often built to announce the arrival of Buddhist monks carrying the Doctrine from India to Southeast Asia or Ceylon. Sizes of the Phra Chedi range from about two meters high to the larger stupas of which may reach up to 115 meters. When newer or larger ones were desired, they were built encasing the old rather than destroying them and starting anew.
The prototype of the Chedi originated in central India. It is composed of: the drum (basement); dome (tumulus); surmounted by a cubical chair symbolizing the seat of Buddha; and over it the chatra (umbrella), which originally only had one tier and later on became a slender pinnacle formed by many tiers. Numerous variations of the stupa exist in Thailand, but they can be limited to these principle types:
Northern Type: formed by a cubical solid mass having four niches at its sides containing images of Buddha in high relief or round relief; this cubical mass is superimposed by one or more stories and crowned by the domed stupa (Figure 1, top image).
Reminiscent of the Sat Mahal Pasada at Polonnaruva in Ceylon, formed by many receding cubical stories enriched with horizontal rows of standing Buddha images in high relief. This type of Phra Chedi is common in northern Thailand (Figure 1, bottom image).
Round-planned stupa having the same elements as the Indian prototype which was introduced from Ceylon. This stupa has a high drum formed by many moldings of the same design, a bell-shaped dome, a square throne surmounted by a low circular colonnade supporting the high and slender chatra (Figure 2, image 1).
Ayudhya period stupa: by adding four niches, borrowed from the northern art, to the dome of the classic Phra Chedi, the Thai composed a newly refined type of stupa form (Figure 2, image 2).