Ratnagiri was established in the reign of the Gupta king Narasimha Baladitya in the first half of the sixth century but it came to limelight in the twelfth century. A large-scale excavation was conducted at the site between 1958 and 1961. The main stupa dates to the 9th century CE and was likely built on the site of an earlier, Gupta-era stupa.
Large number of stone sculptures, few bronze and brass image of Buddha and Buddhist pantheon recovered during excavations tend to prove that Ratnagiri was a great Tantric center of Buddhism comparable to that of Nalanda in Bihar.
Udayagiri, similar to Ratnagiri, it is composed of major stupas and monasteries (viharas). Together with the nearby complexes of Lalitgiri and Ratnagiri, it is part of Puspagiri University. The heritage sites are also known collectively as the “Diamond Triangle” of the “Ratnagiri-Udayagiri-Lalitgiri” complex.This Buddhist complex, preceded by the Ratnagiri and Lalitgiri sites, with their monasteries, is believed to have been active between the 7th and the 12th centuries.