However, according to the Galpotha (Stone Book) inscription, King Nissankamalla (1187 - 1196 AD) constructed Vatadage inside the quadrangle and named it Ratnagiri Vatadage, implying that some restoration or reconstruction work was undertaken here during King Nissankamalla's reign. This, like the other Vatadages on the island, appears as a circular building enclosing a stupa in the middle. Its current shape was most likely the result of repairs or restoration work undertaken in the area of King Nissankamalla or during the Dambadeniya Period (13th century A.D.) when the roof supported by stone pillars had wooden members and was paved with tiles. The Moonstone and two Guard stones to the north and east of the upper terrace can be considered the best examples of their respective types of Polonnaruwa.

The building is built around a small stupa that is 27 feet 8 inches (8.43 m) in diameter at the base. The Vatadage has two levels, the lower platform and the upper platform containing the stupa. The upper platform is 80 feet (24 m) in diameter and the lower platform is 120 feet (37 m). The lower platform is 4 feet 3 inches (1.30 m) above ground level and the upper platform is 5 feet 3 inches (1.60 m) above the ground.

The circular low platform can be accessed through a single door on the north side. The four ornately constructed gates lead to the upper platform, which is enclosed by a brick wall from here. These gates are oriented in four central directions. Around the stupa, there are four statues of Buddha facing each gate. The center of the platform is covered by a stupa. Each Buddha statue is 5 feet (1.5 m) high and is placed on stone seats 2 feet 10 inches (0.86 m) high. There were three rows of concentric stone pillars on the upper platform. None of the two rows inside the brick wall are left, and the third row is visible outside. There were 16 pillars in the inner row, 20 pillars in the middle row, and 32 pillars in the outer row. The existing outer ring columns are about 8 feet (2.4 m) high.