Sanda Hiru Seya stupa was built in commemoration of the fallen war heroes of the Sri Lanka Armed Forces in Sri Lankan Civil War which was ended in 2009.
This is the largest dagoba built in Sri Lanka after the construction of the Jethavanaramaya in Anuradhapura by King Mahasen in AD 301. The pagoda’s structural completion was carried out with the support of hundreds of Army, Navy, Air Force, Police and Civil Security Department personnel of respective security establishments.
The Sanda Hiru Seya stupa is 86.1 m (282.5 ft) high and 240 metres (800 ft) in circumference. Stupa houses sacred relics including the Kapilavastu relics. The height of the Crest Gem placed in the dagoba is 1.1 m (3.5 ft).
There are 1895 gemstones, inlaid with gold as well as pearls.
ref : https://en.wikipedia.org/wiki/Sandahiru_Seya