Ratnagiri, one of the prominent Buddhist centre of Mahayana and Vajrayana learning in ancient India and a contemporary of Nalanda University, is situated atop the flat hillock sandwiched between the rivers Brahamani and Birupa was established no later than the reign of the Gupta king Narasimha Baladitya in the first half of the sixth century CE, and flourished until the twelfth century CE. The constructional activities of Ratnagiri got special impetus under the royal patronage of the Bhaumakaras (9th -10th C. AD). Later, as Buddhism declined in other parts of India, Ratnagiri became one of the last shelters of Buddhism in the country.
On the basis of the sealings bearing the legend "Sri Ratnagiri Mahavihariya Arya Bhikshu Sanghasya," the place has been identified as Ratnagiri.
The finest relic of Buddhist at Ratnagiri is a magnificent doorjamb adorning Monastery 1, one of the two monasteries here. The exquisitely carved chlorite doorframe with gaja-lakshmi on the lintel and the bands of floral, creepers and Gelabai motifs is unique of its kind and marks the highest watermark of decorative art of India. Ratnagiri comprises two magnificent monasteries, one of them was double-storied and had an extensive stone paved central courtyard with two-sides of it having a number of cells for habitation of monks.
The sanctum enshrines a massive seated Buddha in bhumisparsa-mudra flanked by the standing figures of Padmapani and Vajrapani holding chamaras on each side.
A massive image of the Buddha is a unique find which has pursed lips, long ears and wide forehead. Also a life size image of ashtamahabhaya form of Tara (a Buddhist deity) depicted as savior of her followers from eight different hazards and more than two dozen colossal heads of Buddha of various dimensions are found.
Images of Buddhist deities found here show the gradual transformation of the site from the Mahayana to the Vajrayan sect, especially the Kalachakra tantra variety. Numerous references to the site in Tibetan literature suggest that Ratnagiri was an important center in the development of the Kalachakratantra in the 10th century CE, an assertion supported by the discovery of a number of votive stupas, plaques, and other artifacts featuring Kalachakra imagery.
A museum now located on the site displays numerous Mahayana sculptures consisting of colossal Buddha figures, huge Boddhisattva statues, statues of Tara, Avalokiteshvara, Aparajita and Hariti have also been found, all in prototypical of Gupta style. Almost all of these exhibits have an inscription on them.