The Polonnaruwa Vatadage is an ancient structure dating back to the Kingdom of Polonnaruwa of Sri Lanka.

 It is believed to have been built during the reign of Parakramabahu I to hold the Relic of the tooth of the Buddha or during the reign of Nissanka Malla of Polonnaruwa to hold the alms bowl used by the Buddha. Both these venerated relics would have given the structure a great significance and importance at the time. Located within the ancient city of Polonnaruwa, it is the best preserved example of a vatadage in the country, and has been described as the "ultimate development" of this type of architecture. Abandoned for several centuries, excavation work at the Polonnaruwa Vatadage began in 1903. Built for the protection of a small stupa, the structure has two stone platforms decorated with elaborate stone carvings. 

The lower platform is entered through a single entrance facing the north, while the second platform can be accessed through four doorways facing the four cardinal points. The upper platform, surrounded by a brick wall, contains the stupa. Four Buddha statues are seated around it, each facing one of the entrances. Three concentric rows of stone columns had also been positioned here, presumably to support a wooden roof. 

The entire structure is decorated with stone carvings. Some of the carvings at the Polonnaruwa Vatadage, such as its sandakada pahanas, are considered to be the best examples of such architectural features. Although some archaeologists have suggested that it also had a wooden roof, this theory is disputed by others.

Wikipedia