The two most important places of worship in Anuradhapura are the Sri Maha Bodhi and the Ruwanweli Seya (a dome built over Buddha’s relic). The great king Dutugemunu built this gigantic Seya or stupa after saving Rajarata (northern part of Sri Lanka) from foreign domination. The experience and the knowledge he had gained, while he was living in the kingdom of Magama (kingdom of southern Sri Lanka) under the reign of King Kawantissa, helped him to become a great contributor for the Buddhism in Sri Lanka. He built massive structures and developed Anuradhapura into a sacred city of Sri Lanka Buddhism.
Mahawamsa states that monk Mahinda (son of Indian emperor Dharma Ashoka) sprinkled flowers at seven places where future religious buildings would be built and on each such occasion the earth was shaken. When the earth was shaken at the site of the Ruwanweli Seya, Monk Mahinda told the king Devanampiya Tissa, that a grandson of his called Dutugemunu will construct a Stupa at the site in the future. King Devanampiya Tissa built a monument at the location and inscribed the prophecy of monk Mahinda on it.
A popular legend is that there was a Telambu tree (Sterculia foetida) on the very place, where the stupa was to be built and that was the abode of a syvian or a tree spirit named swarnamali. When the tree was cut down it was agreed that her name was to be given to theStupa so it came to be called Swarnamali Seya. The sub commentary to the Mahawamsa mentions that the stupa was constructed above a shallow tank named ‘Kakudha vapi’ (Kumbuk tank). The tank was filled with earth to make a road to Thuparama during the reign of King Lasnji Tissa. Archeologists believe that the low land lying towards the north and devoid of any ruins may have been the tank bed of Kakudha veva.
According to the ancient chronicle Bodhiwamsa the boundary of the Ruwanmaluwa was demarcated by the monk Mahinda himself. The Stupa that was built in the Ruwanmaluwa was the one to be known as Ruwanveli seya. This name however was not used at the beginning and it was known to be Mahathupa or Mahaseya. The name Ruwanveli is mentioned for the first time in the Mahawmasa in connection with the reign of King Khallatanaga. In the rock inscription this Stupa was often referredas the Ratanacetiya. The rock inscription of Kirti Sri Nissankamalla found at the main terrace of the Ruwanveli seya itself bears witness to this usage. An inscription found at the Thuparama belonging to King Gajabahu 1 mentions a grant made to the monks at the Ratana Araba Vihara.prof.Paranavithana has pointed out that this reference would have been very likely applied to the Ruwanveli.
Ruwanveli was known as the Mahathupa as it was the largest in size compared to other stupas in Rajarata. The author of Mahawamsa speaking of the size of the Mahathupa says that the King desiring to allocate a large space for the cetiya ordered a minister to walk around along the ground prepared while he held a turning staff for tracing the circular boundary but a monk named Siddhattha prevented the King the great dimension and got him to allocate a moderate space for the cetiya. This the monk did for he knew that death would come upon the king before such a big Stupa would be finished and moreover it would be a hard task to repair such a big stupa. At last the Mahacetiya with a diameter of about 370ft was constructed on the designated site by the monk Mahinda.Google+