Mahasena builds the Jetavanaramaya

Mahasena reigned 273–301 by one chronology and 277–304 by another; the Mahavamsa, the chronicle of the Mahavihara monks, gives him 27 years. His teacher Sanghamitta followed the Vaitulya (Vetulla) teaching, usually associated with the Mahayana, and was hostile to the Theravada monks of the Mahavihara, the island’s oldest monastery. According to the chronicle, the king forbade anyone to give alms to the Mahavihara monks, the monastery stood deserted for nine years, and its buildings, among them the seven-storeyed Lohapasada, were pulled down and their materials carried off to the rival Abhayagiri. His minister and friend Meghavannabhaya rebelled; on the eve of the battle the two were reconciled, the king promised to restore the Mahavihara, and Sanghamitta was killed on the orders of a queen. Mahasena then built the Jetavana monastery for the thera Tissa in the Jotivana garden, within the boundaries of the Mahavihara, whose monks left their monastery for nine months in protest.

The stupa, finished by his son Sirimeghavanna, is thought to have risen to about 122 m and to contain some 93 million baked bricks; it is often described as the third tallest structure of the ancient world after the two largest pyramids of Giza. The Jetavana monastery belonged to the Sagalika school, closely linked with the Abhayagiri. Restored in the 12th century by Parakramabahu I, the stupa now stands about 71 m high. Mahasena also built sixteen reservoirs, among them Minneriya, and a great canal, and he was later worshipped as Minneri Deviyo, the god of Minneriya.