Abhayagiri monastic complex is a World Heritage Site. Abhayagiriya is the tallest brick edifice of the ancient world with its original height being 350 feet. Abhayagiri Monastery was built by King Valagamba (Vattagamini Abhaya) in the second century B.C. as recorded in the chronicles. It was however during the reign of King Mahasen in the 35 3rd century A.D. that Abhayagiri rose to prominence, growing into an international institution to rival those of Nalanda and Vikramashila, attracting scholars from countries like India and China.
The monastic complex is believed to have covered an area of about 200 hectares in its heyday. Initial archaeological excavations have revealed that it had a well laid out plan with a 320 feet stupa at the centre, surrounded by other religious edifices and residential quarters Besides the central stupa known as the Uttara Maha Chethiya, the complex has four other stups as well as an image House, Bo-tree Shrine , Chapter House, Assembly Hall, Alams Hall and Residential Quarters. Abhayagiri Viharaya is not just a complex of monastic buildings but it is also a place where Buddhist monks maintained their own historical records, traditions and practiced the Buddhist way of life, These practices attracted scholars from other countries and it grew as an international institution of Buddhist philosophy by the first century AD.
The ruins of entrances with decorated steps, moonstones, balustrades and guard stones, ruins of elegantly constructed edifices of the Relic House with delicate sculptures, ruins of the residential complex, ruins of peripheral stupas, ruins of Buddha images, ruins of urinal stones which are elaborately decorated, ruins of the biggest ricebowl in the world, the elephant pond which is equivalent in area to six modern Olympic swimming pools, the twin ponds, are worth studying at the abhayagiri monastic complex
Ven. Fa-hsien, the Chinese Bhikkhu, during his two year period in Sri Lanka stayed in Abhayagiri and noted that every third month of the year the Sacred Tooth Relic was exhibited for 90 days for the public to pay homage. Today it is the site of the Mahatissa Fa-xian cultural Complex which also houses a museum (to house the artefacts found during the excavation) an information centre, a book stall, a storehouse for archaeological finds and a record room and residential quarters for Bikkus built according to the ancient plan of the five-unit complex as found at Abhayagiri. The cultural complex is in fact a gift from China to Sri Lanka.