Dvaraka sinks into the ocean
Dwarakadheesh temple in present Dwarka city, believed to have been originally built by Lord Krishna's grandson, Vajranabha, over the hari-griha (Lord Krishna's residential place)
The account of Dvaraka's sinking into the ocean is found in book 16 of the Mahabharata (Mausala Parva).
Day by day strong winds blew. Earthen pots showed cracks or broke from no apparent cause. Society became corrupt. The day of the new moon coincided with the thirteenth (and the fourteenth) lunation. The fourteenth lunation has been made the fifteenth by Rahu once more. Such a day had happened at the time of the great battle of Bharatas. (Kurukshetra War). It has once more appeared. After that war 36 years had passed. The messengers proclaimed at the command of Vasudeva Krishna that the Vrishnis should make a journey to the seacoast for bathing in the sacred waters of the ocean. (16.2)
The Yadavas, then, with their wives, proceeded to Prabhasa and took up their residence there, each in the (temporary) habitation that was assigned to him, and all having an abundance of provisions consisting of edibles and drink. The Vrishnis, mixing with wine the food that had been cooked for high-souled Brahmanas, gave it away unto monkeys and apes. Those heroes of fierce energy then began their high revels, of which drinking formed the chief feature, at Prabhasa. Then a dispute arose between Satyaki and Kritavarman on the wrongs they did in the Kurukshetra War. This dispute turned into a great massacre, in which all the Yadava heroes were slain. (16.3)
Arjuna arrived at Dwaraka and addressed the chief officers, to prepare to leave Dwaraka within 7 days, as Dwaraka is going to sink in the ocean. Krishna's grandson Vajra was chosen as their king to be ruled at Indraprastha. Arjuna then proceeded to the place where the Vrishnis were slaughtered. Searching out the bodies then of Bala Rama, Arjuna caused them to be burnt by persons skilled in that act. On the seventh day, Arjuna evacuated Dwaraka Island. After all the people had set out, the ocean flooded Dvaraka, which still teemed with wealth of every kind, with its waters. Whatever portion of the ground was passed over, ocean immediately flooded over with his waters. Beholding this wonderful sight, the inhabitants of Dvaraka walked faster and faster. (16.7)
Pandavas on their last journey before death, saw Dwaraka covered by ocean (17.1)