The abode of Hindu deityJagannath at Puri is known as the Nilachala or Niladri, meaning, The Blue Mountain. The Nilachala is a place of high religious significance in Hinduism and is one of the four Char Dhams. Religious teachers like Shri Ramanuja Acharya, Swami Vishnuswami visited Nilachala in the Twelfth century and established a mathas. Shri Nimbarka Acharya also visited Puri, as also Guru Nanak Dev and many other Acharyas. Shri Chaitanya spent 18 years at Nilachal dhama. As per religious texts and the Skanda Purana, mythical KingIndradyumna of Avanti once dreamt of the great deity Nila Madhava being worshipped at the Nilachal mount. The King sent out many priests and messengers in the search of the elusive deity Nila Madhava. Finally, Vidyapati, one of the priests of King Indradyumna located Nilachala as well as Nila Madhava at the Purusottam Kshetra and took the news back to the King. However, as per divine designs, the Nila Madhava deity vanished before Indradyumna could undertake darshan. But, subsequently, propitiated, the God appeared as Jagannath at Nilachal. Geographically, though, there is no such apparent geographic structure at Puri, the township being located at the coastal plains of Eastern Odisha. Such a reference to a seemingly non-existent mountain has been a matter of debate which throws light on the origin of the deity.
Hypotheses regarding existence of the Blue Mountain
Yet contrary to such opinion, the platform of the Jagannath temple, seems to be a totally man-made monument, not a modified natural hill. The Nilachala consists almost entirely of a platform, and at its north—western foot lies an artificial cave. This is approximately 25 feet below the level of the inner enclosure, for a staircase of about twenty two steps leads down to the sanctum of deity PatalesvaraShiva, and gives some idea of the level of the original terrain. The site was obviously exposed to flooding during the monsoon season as once the river touched its lowest steps when it flowed in the broad road just in front of the temp
Hypothesis 2
Another hypothesis regarding the naming of Puri as 'Nilachala' has been advanced by the noted historian, Dr. Krushna Chandra Panigrahi, in his "History of Orissa", pp. 338–339. It has been argued that no mountain existed at the Jagannath shrine, and:
""Then the Bhaumas came from Assam in the first part of the eighth century A.D., ruled over Orissa, obtained the shrine from the Savaras, got the temple built on the spot and gave it the name Nilachala, which was the name of the famous shrine of Kamakhya in their homeland of Assam."."
In the 19th century, certain scholars have imagined that the Nilachala concealed the debris of a former Buddhist monument named Dantapura. However, Puri cannot be identified with Dantapura and so far no Buddhist remains have been discovered there.
