Vatadage
It can be observed that after the 4th century, the building of colossal dagobas has virtually ended. Thereafter smaller ones have been built using Thuparama in Anuradhapura as a model. This type came to be known as ‘vatadage’ or rotunda. It is a circular relic house and apart from Thuparama and Lankarama in Anuradhapura, the best example is seen in Polonnaruwa.
There are two other beautiful ones at Medirigiriya close to Polonnaruwa and Tiriyayi off the Anuradhapura-Trincomalee road. These circular shrines enclosed stupas of smaller size and had wooden pillars right round. Later they were replaced by carved stone pillars. The pillars are arranged in four to two concentric circles, diminishing in size outwards.
Read more about this topic: Ancient Stupas Of Sri Lanka