Ratnagiri is one of the three hills of the Diamond Triangle, others being Lalitgiri and Udayagiri. It is situated on the banks of the Birupa River, in Ratnagiri village, Cuttack District of Orissa. The Diamond Triangle and its surroundings are noteworthy, with a remarkable Buddhist complex, dating back to the first century.
Initially, Ratnagiri was a prominent Buddhist center, especially of Mahayana sect and later became a great center of Vajrayana Buddhism in the 8th – 9th century. According to Pag Sam Jon Zang, a Tibetan source, the institution at Ratnagiri was responsible for the emergence of Kalachakratantra in the 10th century, the fact of which is substantiated by the votive stupas revealed from the site. Two large monasteries, Buddhist sculptures, inscribed stone slabs and molded terracotta plaques were unearthed from here.
The university, though in ruins, is noted for its beautiful doorways and sanctum with a colossal Buddha figure. Other highlights in the site include a small monastery, stone temple and a large stupa.