From The Dhamma Encyclopedia
The Ruwanwelisaya (also written as Ruvanvalisaya) is a stupa in Sri Lanka, considered a marvel for its architectural qualities and sacred to many Buddhists all over the world. Simply known also as the Great Stupa, the Ruvanvalisaya was constructed by Dutthagamani after he became king in 161 BCE. This was his most ambitious project and it is said that one of the architects designed the dome to resemble a bubble of milk. Sadly, the king did not live to see the completion of the stupa.
When it was finally completed, it was one of the wonders of the ancient world, with a diameter of 90 meters at the base and a height of 92 meters (300 ft) and circumference of 292 meters (950 ft). The stupa is one of the world's tallest monuments and was the fifth tallest structure of any kind when it was built in approximately 161 BCE.
The compound of the stupa is surrounded by four walls with elephant figures made into them. It is believed that relics of the Buddha are enshrined within the stupa. The Ruvanvalisaya was also designed with the teachings of the Buddha in mind. Its dome signifies the vastness of the doctrine, the four facets above it represent the Four Noble Truths, the concentric rings indicate the Noble Eightfold Middle Path, and the large crystal at the pinnacle represents the ultimate Buddhist goal of enlightenment.
The stupa is also one of the Solosmasthana (the 16 places of veneration) and the Atamasthana (the 8 places of veneration in the ancient sacred city of Anuradhapura). The entire city of Anuradhapura has been designated a UN World Heritage Site.