It is believed that Vessagiriya is the Issarasamana Viharaya, where 500 Buddhist Bhikkhus of the first Bhikkhus in the country who entered in to the Sasana with the Minister Aritta of King Devanampiyatissa (250-210 B.C.) in the 3^rd Century B.C.

The King and his Ministers had constructed caves and donated them to Buddhist Bhikkhus (Agata anagata chatudisa sagasa dine) present and not present, coming from the four quarters of the country, for them to reside and do their meditation. More than 65 caves here contain inscriptions dating from the 3^rd C.B.C. and later other kings too gave donations and added many buildings to this monastery, which is spread in an area of 100 acres.

King Kasyapa I (473-491 AD) renovated this viharaya and named it as “Boupulvan, Kasubgiri Radmaha Vehera”. This name is derived from names of his 2 daughters and his name.